TLDR: All are extracts from the cannabis plant. They differ by purity and some may contain trace amounts of THC vs. pure CBD. Isolate is the purest, followed by distillate, which is used to make Broad-spectrum preparations vs. Full-spectrum which retains all cannabinoids, terpenes, waxes, lipids.
So why all the confusion?
There's a lot of marketing jargon and gimmicks to sell a particular product. All these terms have been created to describe cannabis extracts, degree of processing and refinement, and overall purity and concentration.
To start with, most cannabinoids are extracted using either super critical CO2, ethanol, and sometimes using butane which strips the organic plant matter of cannabinoids, waxes, lipids, and cells.
This semi processed extract is then further processed through fractional distillation which brings each cannabinoid to its boiling point and then condensing the vaporised cannabinoid. This process is repeated until a desired purity is reached and all the ethanol, CO2, or butane is removed.
The highest purity product from fractional distillation is Isolate, which is often 99% pure and results in a solid block of crystal that is then turned into a powder. The isolate then can be prepared into oils, food, drinks, and vaporiser products. Isolate is ideal for users who react negatively to THC.
Second highest in purity and range between 60% to 85% and contain a broad-spectrum of cannabinoids, and terpenes. The ratio of cannabinoids can even be tweaked as they are recombined and mixed into specific formulations.
Broad-spectrum refers to preparations which contain a broad range of cannabinoids vs. Isolate which is just one cannabinoid. Broad-spectrum products are typically made from Distillate as per ratio of cannabinoids required.
Full-spectrum is when all the cannabinoid, waxes, lipids, and terpenes are retained from the original plant material. This can be desirable for some users who prefer the range of benefits of each cannabinoid present in the plant material. This means sometimes, full-spectrum may contain illegal trace amounts of THC, which remains a controlled substance here in the UK.