zirkonflex
You name it
Blablbabla ... Mic ... Line Input ... blabla
You actually put mics into the mic in if you don't have a pre
But seriously thats like the most important part of any kind of studio at all.
You atleast need a decent USB interface (No wierd Toneport or shit), face it.
It will will cost you 150-350 bucks but you can't do without.
Its gonna be used for all the guitars and basses (if youre going digital), and it will have 2 to 8 good mic ins that you will probably want to use more and more the further you get into the recording stuff.
My suggestion for someone starting recording would be getting a USB Interface (lets say 200 for it), then "get" some software and some superlux headphones (can't recommend them enough) as well as some cheap mics (Probably T-Bone or whatever).
Depending on the amount of inputs of your USB device and the mics at your disposal you'd be able to flawlessly record entire albums from scratch with such a setup, if you get some experience you could even make it sound killer as hell.