Exactly what do companies like Prudential, Merill Lynch, and Lehman Brothers do?

Question

What sort of services do they offer? What separates them from ordinary banks like Citigroup and Bank of America? Are there any requirements to be a client? Can non-Americans be their clients?

Answer 1

well they are investment banks that have huge capital and underwrite company's IPO (so does citi and BOA) they offer investment packages like fidelity so basically they buychunks of stock that their customer buy (i.e on the floor of the NYSE) and of course they have foreign clients