My understanding is that the mechanism is different from bica, spiro, and cypro and that it's not really an anti-androgen, just something that can be used to supplement them. From what I can gather, finasteride stops your body from converting testosterone to DHT. DHT is a much stronger version of testosterone, which is converted from testosterone using a chemical called 5-α-reductase which is produced by the body. However, while DHT is stronger than testosterone, it doesn't travel around the body as easily and tends to concentrate in the places where it's made, which are the tissues that produce 5-α-reductase, and that's where it has noticeable effects. Finasteride works by reducing the amount of 5-α-reductase produced by the body, which reduces the amount of DHT in those tissues, essential reducing the effect of testosterone on those areas.

However, because the effects of DHT are local, the effects of finasteride are also limited to those tissues which produce 5-α-reductase (I think mainly hair follicles, but I'm sure other stuff too). Because of that, although it can help with hair loss, it doesn't really reduce the effects of testosterone on the rest of the body, and in fact it's primary use is for preventing hair loss in cis men, precisely because it doesn't reduce their testosterone. So you might take finasteride for hair loss or other stuff, but you still need another anti-androgen unless you're doing estradiol monotherapy.

As for bica, spiro, and cypro, bicalutamide works by just preventing testosterone from having any effect on your body, cyproterone acetate directly stops you from producing testosterone, and I think spironolactone actually works by a mixture of reducing how much testosterone you produce and reducing how much it's absorbed by the body, although I could be wrong about that.