The question of stereo/ mono comes up around here quite often, as well as the confusion surrounding those terms.
Here's a
LINK as an example.
As a newbie you could benefit from having some terms defined:
When we talk about "tracks" in recording, we usually mean a channel of audio that is recorded that represents an individual instrument like Kick Drum, Bass Guitar, Vocal, etc. For the most part these don't need to be recorded in "stereo", although they can be.
Some of the multi-track softwares have the ability to record a "stereo track", which means you would be recording a left and a right channel of information. To me this is confusing for the newbie, because a "track" to most recording people indicates a Mono recording! Mixdown was always refered to as going down to 2-track, not down to 1 stereo track! Anyway. . .
Every CD you listen to has a Left and a Right channel. When you play back on a boombox or car stereo or Hi-Fi the sound from each channel (or track

)goes to each speaker, left and right.
So in the recording world, things that are listed as "Two-Channel" are usually designed to work both as "Stereo" (like for a mixdown) or as two channels, one for guitar, one for vocals or whatevah.
if you use both plugs, does that make it stereo and if you use one does it make it mono?
If for instance, you were to record a vocal with one microphone, then used a Y splitter to get the signal from the pre-amp to both inputs of your sound-card, this would be pointless, since you are recording the same identical sound to 2 channels of audio, when you need only one! It wouldn't be any more "stereo" at all!
You will be using twice as much space on your hard drive, for no reason. You just hook up to one input, then tell the software you are recording a mono source. Then on playback you will pan the signal to the center to get sound out of both sides.
And yes RCA jacks/plugs are sometimes called Phono jacks/plugs.
XLR is a balanced type connection found on mics, and some gear, although an XLR in on the back of something doesn't always mean it's for plugging in a mic!
TRS means Tip, Ring, Sleeve, and is used as balanced connections too, but sometimes it can be for an insert (send and return on one plug) or a headphone jack. Looks like a guitar cable end with an extra ring on the sleeve.
TS is a standard 1/4" plug, for guitars or instruments.
Ah if there were more time, I'd go on
If I confused anyone I apologise in advance.