Can someone explain simply in weekend warrior car mechanic's terms what a boost a pump is and when you need it? Obviously you need it when you need more fuel delivered and you are making more HP aka boost or whatever but do you need a boost a pump in EVERY situation where you are getting more power and fuel to the engine? How is a boost a pump different than just getting a better fuel pump and injectors? I know injectors are front end kind of like getting a bigger spray nozzle on the garden hose, and the fuel pump would be the pump that send the fuel. SO where does the boost a pump fit in into this picture?
And what IS IT exactly? is it an electronic module or some mechanical device thing?

Do you need a boost a pump for any turbo or supercharger system even if you are pushing 5-8 psi or whatever is recommended safe on stock internals?

Particularly asking about the 99-04 Mustang GTs but I imagine this would be universal to many cars.