Retirement tax questions

I'm afraid I still don't get it. If the maximum I can defer to all my 401(k) plans is, according to TurboTax, around $25,000, and/but I'm allowed to put a maximum of almost twice that amount, into my qualified plan as profit sharing, can you tell me what the actual options I'm being given look like? If I'm being given an option here, why would one choose one or the other? Sorry if I'm being a bit dense. Thanks for helping.