Pawn Diagonally Movement

I was playing against the computer when it suddenly made the move cxd6 with its pawn, is this a version of en passant? I thought it was only regarding capturing

It didn't let me make the cxd6 pawn move, so i'm assuming its illegal? why would the computer allow it in a practice game?

Not exactly sure what you mean.  On move 8, you can use your e5 pawn to capture the black dpawn, moving your pawn to d6, and removing the black dpawn, which is a totally legal use of en passant.  If you really mean your c-pawn, which is what you said, you are badly confused.  En passant literally means "in passing", and what you are doing is in effect capturing the black pawn "in passing" -- i.e., as it passes through the d6 square, which is something that only the epawn is in position to do.  

On move 8, in response to my castle, the computer moves their c7 pawn to d6, i couldnt show it here so i assumed it was an illegal move but i dont know why it was done

I took a screen shot of the move but im on mobile

That would be a bug.  

Thanks bud i was really confused and im not the greatest so i thought it might be something i didnt know

Nope, that was my first try at easy. Im getting matched aginst ppl from 490 to 650 in blitz and wanted to see if the computer made some of the same moves as my opponents.

Not a bug - its happened to me many times and have no idea why

played chess 50 years before joining Chess.com and never saw a non-en passant diagonal pawn move before so better ask Chess.com's programmers

My guess is that it was a glitch in what your screen was displaying, and that the actual move it made was different.  The usual suggestion is the clear the cache so it uses fresh images for everything instead of using possibly incorrect images that were stored locally on your device.

could be - its hard to focus on all the pieces simultaneously - lots of images stick in the eye

no chance to replay in live games to check without messing up

never mind.