Why can't I kill a piece that puts me in check?

I can explain what castling is, but it might make more sense if you watch this 3 minute video. https://www.chess.com/lessons/castling

Thanks, I'll watch it so my original first question though, that's called a discovered check ? I still don't really get it.

Oh my God this thread!!!

Yes, it's called a discovered check.

No. White queen on e2, black king on e6

Gee, you sure have experienced a lot in the 1 hour since you signed up for chess.com...

@hazyeyed Yep! The answer to the original question is the discovered check.

The queen was lined up with (aiming) at you king - the only thing in the way was white's knight. Once white moved the knight, there was nothing between your king and white's queen. So white's queen put you in check by moving her knight out of the way. 

Are you confusing king with queen?  Look at the picture:

The king has the cross on his head.  The king was attacked by the white queen on e2, so you moved out of check to d7.  The queen, the the 4 pointed crown, at the same time, was attacked by the white knight.  An attack on the queen is not check, btw.  You wanted to take the white knight with your knight, but that didn't work because you have to get out of check from white queen.  You couldn't save your queen and get out of check all in one move, so you lost your queen.  

Well, you can't "kill" pieces so it does read like it's a little off, and usually people will post a position with a question.

There are situations where you can't capture the piece putting you in check. Off the top of my head:

1) The piece putting you in check is defended
2) The piece you want to capture with is pinned
3) You're in double check (being checked by two pieces at once)

Anyway, from your terminology, it seems you're a beginner, and so in a game where you couldn't capture a piece putting you in check you probably didn't notice one of those 3 things. Lots of beginners post question about "illegal" moves when they just weren't looking at the board very carefully.

Lol are you trying to confuse the poor OP even more or something

Yeah, that's what they call it. Maybe a more literal term would be "uncovered" check because the piece that's been covering the queen (see below) has been removed, so the queen's attack now reaches all the way to the king.

I always called it "revealed checks" - since I'm kinda self-taught - like, the knight moves, revealing the check.

I use Google to search for real sources. Of course, it is easier to use Google well after you have learned to separate bogus information from credible. From what I can see in your screenshot is enough to remind me why I've never been to jimmyvermeerdotcom. It's obviously the work of a child who doesn't know the subject.

I learned chess from people who know how to play, not from internet posers. I play tournaments with real people, some of whom are titled players. I teach chess.

Google points me to: https://www.fide.com/FIDE/handbook/LawsOfChess.pdf. My search was not "can I kill a piece checking me".

BTW, most of the responses in this thread are from people who know what they are talking about. One has even found the game that you referenced and explained it to you. It's clear that you are just beginning to understand some of the rules and still have more to learn. Chessdotcom is a good place for you to learn. Maybe watch some of the beginner's videos.

People are hyping this up way too much. https://gyazo.com/a039c0284c59649f4894b0283774f4c1 There is nothing wrong with this link, it is entirely accurate so far, and being taken out of context. You can see only a part of what they are saying, and none of it is wrong.

https://gyazo.com/257f5c4946c35a8e87fb42261846a8b9 In this link you cannot take the knight as black because it is not your move, it shows black just moved. If we rewind to the move before, the king is shown to have been in a square where the queen is putting the king in check, taking the knight would not take the king out of check, so it is an illegal move. 

This is a legitimate question.  I would have written "poseur" instead of "poser" since I find the word "poser" can have other denotations as well as connotations, while "poseur," while being French, seems rather definite in both.  Do you know if one is more acceptable than the other in English? 

By "people", you mean me. No one else has criticized the OP's use of Google.

Let me be more clear:

The quality of the search has two problems:

1) The OP used improper terminology ("kill"), which leads the search engine to return poorer quality responses, and

2) Skipping over the first two hits in a Google search is a standard practice for anyone who understands how to use the tool.

Nonetheless, there is a more significant problem.

Even the poor use of the tool (a search engine) led to information that could have corrected the OP's misunderstanding. However, the OP does not understand chess well enough to comprehend the information.

Most posters in this thread have been very helpful, it seems to me. If the OP takes the time to read the responses carefully, the rule and a better move in the referenced game should become clear.

I agree with your assessment of the second link.

You are correct, but sometimes perverse connotations are part of the intent.

I've always used the American version of the word. I'm a gun totin' western American liberal redneck. French ain't my language.

Poseur is less problematic unless one already has a reputation for being too erudite, i.e., "arrogant" in a chess forum.

Damn it!!! Arggggh

Well, I sure don't tote guns. Sometime I tote a water bottle.  Being too erudite has definitely never been one of my character flaws.  
Thanks.

When batgirl gets serious, she totes pens, keystrokes, and historical records.