It's best, in this age of information overload, to avoid gullibility in everything. This approach is especially necessary for the complementary health industry, including the now-burgeoning hemp cannabidiol (CBD) commercial market. Unfortunately, the market still tends to take liberties with unsupported CBD oil "facts."
After nearly seven decades, commercial industrial hemp and all its derivatives are finally legal in the U.S. again. But this is a very recent development, and state governments are still shuffling around to get their regulatory houses in order.
So, because the market is still largely unregulated, many of the so-called "CBD oil facts" online and in the media are probably best viewed with a questioning mind.
What is CBD good for? Well, a multitude of things, it turns out. Hemp, or cannabis, has had medicinal utility for mankind for millennia already. So, these remedies are really not new.
CBD itself has furthermore been fairly well studied the past twenty years or so, but there are still no official guidelines available for its use. Consumers in the U.S. are waiting for the FDA to determine these, but their formulation entails a process that could still take years.
In the meantime, prospective users are left to their own devices, and self-education with experimentation is probably the best way to go.
Here we help the reader to separate the wheat from the chaff with these research-backed facts about cannabidiol.
Fortunately, medical investigation has been confirming for a while now that CBD oil is completely safe to use.
As a fairly extensive, recent review of the literature concluded:
"... the often described favorable safety profile of CBD in humans was confirmed and extended by the reviewed research."
CBD even proved to be better tolerated than many pharmaceutical drugs. So, in most cases, users can now experiment with CBD oil without fear of harm and with impunity.
Yet the same authors also stress that a lot more research is needed, especially in areas such as the cannabinoid's liver metabolism, drug-drug interaction, and "some important toxicological parameters," such as its effects on hormones.
So, while CBD seems, for all intents and purposes, to be a benign, trusted remedy (also based on a large body of anecdotal evidence), much study is still called for. 
Cannabidiol's efficacious utility has been fairly well-demonstrated in both clinical and animal models.
The largest body of research material deals with anxiety and related disorders. CBD's positive pharmacological effect is one of the best studied so far.
A 2015 review of the literature found that existing preliminary study strongly supports CBD's efficacious use in anxiety disorders, including:
Effects were noted in the listed conditions with acute dosing only. The reviewers observed that evidence is lacking for CBD's chronic use. 
This is not a new application of CBD, and many U.S. states are already allowing its possession and use for some (or all) of these conditions. This would be primarily as part of their Medical Cannabis Programs.
Another double-blind, placebo-controlled study investigated the neurology behind CBD's anxiolytic effect in patients with a social anxiety disorder (SAD).
Employing functional neuroimaging, CBD was shown to have affected the limbic and paralimbic brain areas (both are involved in mood and emotional regulation) of all the subjects. For the research team, these results indicate that CBD reduces anxiety in SAD. 
Users report feelings of relaxation, calm and well-being, which supports scientific evidence that indicates cannabidiol's possible therapeutic application for depression, too. Depression and anxiety often present together in mood disorders.
So far, not that many clinical (human) studies have been done to test CBD's antidepressant effects. However, animal studies are conclusively showing that it has functionality in this mood disorder, too.
For instance, one study had the objective of observing CBD's effects on depression in a rat model. The conclusion?
"These results suggest that CBD may be beneficial for the treatment of clinical depression and other states with prominent anhedonia." 
Anhedonia is the inability to feel pleasure.
Another review, focusing only on animal studies that investigated CBD and depression, reports that CBD exhibited antianxiety and antidepressant effects.
The reviewers also note that most of the studies demonstrate a good interaction between CBD and the 5-HT1A neuro-receptors. Activity of these receptors in the brain is implied in many treatment models of depression. 
Yet another study looked at CBD's ability to help with depression brought on by pain. Which brings us to yet another of wondrous CBD's indications. 
The relationship between depression and pain is not unknown and has been confirmed in numerous preclinical studies. Also, many people suffering from this particular comorbidity don't respond well to mainstream pharmaceutical therapies.
It is furthermore considered a cause of high mortality in this population. 
Together with the body's own endocannabinoids, as well as CBD's popular but notorious family member—tetrahydrocannabinol (THC), cannabinoids are known not only to decrease depression but also to manage pain. This they do via the body's endocannabinoid system.
As the authors of one review explain in their conclusion:
"The endocannabinoid system is involved in eliciting potent effects on neurotransmission, neuroendocrine, and inflammatory processes, which are known to be deranged in depression and chronic pain." 
Pain is also often related to inflammatory conditions.
One 2010 review notes that CBD works, again in tandem with THC and other compounds, to address inflammation. The authors comment:
"Cannabinoids suppress inflammatory response and subsequently attenuate disease symptoms." 
An animal study, however, seems to suggest that CBD alone could have a therapeutic effect in arthritis (an inflammatory disease) to attenuate pain and inflammation. This was affected by applying a topical CBD preparation to the sites of inflammation, which holds so much promise for its therapeutic use. 
Most pharmaceutical anti-inflammatory drugs are known for their harsh side effects, including gastrointestinal disturbances. Applying a CBD cream to the skin will bypass these side effects.
Chronic inflammatory conditions and epilepsy are also two well-known indications for treatment with CBD.
In fact, by now it is old news that the FDA has approved America's first CBD-drug for epilepsy last year. Its indications are for severe seizure disorders—Lennox-Gastaut and Dravet syndromes—and its use is safe even for children as young as two years old.  
What is CBD good for? Well, a lot more (especially clinical) research is necessary before this question can be answered with certainty. Yet currently, the solid CBD oil facts are pointing in a positive—even exciting—direction for medicine, especially now that hemp CBD should be easier to research.