Full spectrum oil is CBD oil in its most raw form, "crude" oil.  It contains fats, waxes, lipids, terpenes, and a range of other cannabinoids such as CBG, CBC, CBN, and THC.  Isolate is the purest form of Cannabidiol, it is a highly refined crystalline powder, typically 99.9% CBD with no other plant compounds.
Research has suggested that full-spectrum CBD tinctures may offer advantages over Isolate CBD tinctures.   This is because of a phenomenon known as the “entourage effect” – the appearance that CBD works better in the presence of other naturally-occurring hemp compounds, rather than by itself (regardless of potency).