Cannabis and hemp plants contain over 100 compounds, with CBD and THC being the most prevalent. All of these compounds can be beneficial, although a lot depends on the concentration levels, and condition they are being used to treat.
Pure CBD oil is solely the CBD compound.
Broad-spectrum CBD oil will contain other compounds, although usually with the THC eliminated.
Full-spectrum CBD oils contain all of the terpenes and compounds, including THC, so care is required to verify the concentration levels, as THC over a certain level is illegal in the UK.