Phono Inputs...what can I use them for?

Hey everyone.

Today is the day for stupid questions. Here's mine.

I've got a vintage Sansui AU-717. I love it. It's the first non-crappy piece of audio equipment I've ever owned. But I'm long past my listening to vinyl days, and I've got this great integrated amp with not one, but two phone inputs. What can I use them for? I understand they're a bit different than the AUX input. Something about voltage...

Could I use them to plug something else into? TV? MP3 player? CD/DVD player? What are their limitations?

Thanks!

James