To clarify the types of brake fluids, there are three types, Mineral (specified by certain car manufacturers, eg. Citroen, etc), Synthetic (the standard type of brake fluid) ... and Silicone.
If you go by the DOT number you cannot go wrong, up to and including DOT4 is a synthetic man made product (but not containing Silicone).
There is a misunderstanding between synthetic and silicone. Look at containers of DOT4 and they often carry the word 'synthetic', because that is what it has always been, but NOT silicone. Years gone by its major ingredient was vegetable based. Refer by the DOT numbers and you cannot go wrong.
DOT5.1 is a silicone based fluid, but not fully silicone. I would only use it where specified by the manufacturer
DOT5 is fully silicone