Full-spectrum CBD oil contains more than just CBD. It includes many other cannabinoids and terpenes (including trace amounts of THC – tetrahydrocannabinol) that combine to create an “entourage effect” of compounded benefits, activating the CBD for best efficacy in the body.
Broad-spectrum CBD oil is similar to full-spectrum except it does NOT contain any THC whatsoever. It is not recommended unless someone absolutely cannot have THC in their bloodstream.
Isolate is just what it sounds like: pure CBD, stripped of all the other chemical compounds. The removal of these other compounds means no entourage effect and noticeably reduced efficacy.