Threads
Here's a little primer on threads. You may find it useful.
NPT (national pipe thread) is the standard pipe thread in the USA. FPT (FMPT) and MPT (MNPT) simply denote female or male. Virtually all the NPT threads that you will find are 'tapered'.

BSPT (British Standard Pipe Tapered) or BSPP (British Standard Pipe Parallel) are the common pipe threads used in England and also in Europe. 'Metric' is a broadly used term to describe not only these threads but also other 'metric' threads used in Europe. The threads on our Italian equipment are BSPP although you will also see them called GAS. For example the spigots on small Italian tanks are BSPP.

Fittings with BSPP threads as well as adapters to NPT are available at places like McMaster-Carr. The bad news is that these adapters are quite expensive. The good news is that you rarely need an adapter because NPT fittings work just fine with BSPP or BSPT in almost all applications for winemaking or brewing. [You may read that you should not mix BSPP with BSPT or with NPT. You can ignore this warning if you are not using high pressure.]

The good news is that you can often mix NPT fittings (which are generally inexpensive) with BSPP or BSPT. For example, 1/2"NPT fittings work just fine with 1/2" BSPP (the thread on the small tanks). In this case, you are mixing tapered with parallel, so use teflon tape. The same is true for 1" NPT with 1" BSPP (the large tanks or the inlet/output of the small self-priming pump).

Tapered vs Parallel Threads.
If you look at male NPT threads, you will notice the diameter of the fitting is tapered, narrowest at the end. Parallel threads do not have a taper. The most important thing to understand is that tapered threads form a seal differently than parallel threads. Fittings with tapered threads seal on the threads. Use teflon tape on these type of threads to help make a good seal. On the other hand, parallel threads can either seal against a gasket or oring--do not use teflon tape--or on the threads--use Teflon tape if you want to seal on the threads. Garden hose thread GHT is another example of a parallel thread--the seal is made against a gasket---don't use Teflon tape.

Gas regulators connect to cylinders thru parallel threads. Do not use teflon tape.

Why does NPT work with BSPP?
Take as an example 1/2"NPT vs 1/2"BSPP. Both have 14 threads per inch so they match up quite well. The primary difference is in the pitch (angle of the thread) which is 60° vs 55°. Use a little teflon tape and they screw together and seal just fine. 3/4"NPT works well with 3/4" BSPP as well since the threads per inch is the same, 14.