I don't speak Italian, so I can't believe that I actually know the answer to this...
There's an Italian word (marinari, marinaro, or something) that means "sailor". Marinara sauce got it's name from that word, because it is traditionally made with anchovies and was commonly made by people who lived by the ocean shore. Unfortunately, there are a lot of "undeducated" people that believe this to be false and say things like "marinara sauce doesn't have seafood in it". The correct statement would be, "marinara sauce doesn't have to have seafood in it". That's just how it is traditionally made.
Also, the difference between marinara sauce and "pasta" sauce is that marinara sauce never has meat in it.