Mistakes are errors, blunders are catastrophic errors at least according to the Hal 9000 here or whatever super-secret PC and program is being used. I use the PC analysis here frequently because it's fast and way better than nothing, but I take a lot of it with a grain of salt. Eventually you gotta start doing your own analysis and using a known program (Fritz, Houdini, Rybka, or whatever) as well where you can control the amt of time spent per move or game, the depth of ply search etc.
Click on "help" in between your name and logout at the top right hand corner of your screen, you'd be surprised how many questions you'll be able to answer yourself.
http://support.chess.com/Knowledgebase/Article/View/153/0/in-the-computer-analysis-whats-the-difference-between-inaccuracy-mistake-and-blunder
http://support.chess.com/Knowledgebase/Article/View/120/0/what-do-the-computer-evaluation-numbers-mean-like-225
I noticed there are two kinds of wrong moves the Computer picks up on when it does your analysis: Mistake and Blunder.
What constitutes a Mistake or a Blunder?
Is a Blunder something like when I miss a mating sequence or when I miss winning material in say 3-5 moves?
What are the specifics of what constitutes a mistake/blunder when it comes to the chess.com computer analysis?
I thought It would be good to know exactly what a these terms mean.
Any answers appreciated.