A petrol filter catches rust and dirt particles from the petrol tank and prevents them from continuing their journey into the engine. Injectors and carburettors continue to run undisturbed this way, which of course leads to more motoring pleasure.
The fuel tap is standard on every motorcycle or scooter. It is possible that in time it stops performing perfectly. Petrol will then continue to flow through to the carburettor and engine, causing your petrol tank to empty more quickly or your motorcycle to refuse to start because it (or she?) is flooded with petrol.
Replacing an original fuel tap can be expensive. Fitting an extra tap is an alternative and in any case a lot cheaper.
The most important information to keep in mind - both for fuel filters and fuel taps - is the diameter of your fuel line.