Korean Non-Polite Endings

I just learned of some NP endings for Korean, 니 & 야/이야.

니 (ni) is used when generally asking someone you're close to (friend) a question.
Examples:
어디 가니? Where are you going?
 점심먹니? Are you eating lunch?

Sounds pretty simple if you ask me.

Then comes 야 which is apparantly used if you have something to express, giving background info, or have a comment.
Examples:
여기가 짐이야 -- Here is home
저기는 꽃가게야 -- Over there is the flower shop
Oh, 야 is used after vowel sounds and 이야 after consonants.

This clears up the confusion behind when I was reading Korean online I'd see ya, iya, or ni after the verb and think ''what is that?" Though I need to practice ya/iya since these two confuse me.