what is the difference between a mistake and a blunder?

What's the difference between a waffle and a pancake?

A cupcake and a muffin?

I mean when you really think about it, aren't they the same thing?

Not on mine. I just looked at a game I thought I played poorly and it classified moves that were 130, and 180 centipawn as inaccuracies. Which I thought was BS, which is why I looked up this thread. 24, 30, 35, 80 centipawn losses were rated 'good'. This would suggest that either the algorithm is changing or more likely it takes into account how good you are. I'm rated 1300+ in blitz and cjxchess17 is rated like 2000+

Additionally, on a blunder I had a +1300 move that was still 800 less than a +2100 perfect move, (ie 800 loss) and it rated it excellent anyways. So the algorithm goes one step further and probably considers if you are doing the second, third, fourth (etc) best move, beyond just calculating centipawn loss. Either that or they are looking at centipawn losses as a percentage of the best move.

It would be nice if chess.com posted some guidance.

It depends on context. A mistake by White changing +11.6 to +9.8 is an inaccuracy, while going from +1.2 to -0.3 could well be a blunder.

The most common definition of a blunder is: a mistake which reduces a win to a loss or draw, or a draw to a loss, by a player who would reasonably not be expected to make that blunder. As you can tell, this is subjective. Either way, a blunder is a severe type of mistake.

Or a blunder can turn a win into a draw.

It's based on criteria input by a programer (Only the programmer knows the basis for the criteria).  Sometimes it doesn't make any sense.  For example, I recently played a game where I was so far ahead, it was almost impossible to lose.  I saw a way to checkmate my opponent that took six or seven moves.  When the game was analyzed by the computer, my move was labeled a blunder because I missed a checkmate in two (I didn't bother to look for it after I saw a way to checkmate my opponent).  My move wasn't a blunder as it had no negative impact on my game.  But, it probably met the criteria input by the programmer.

I don't worry about the label that the computer assigns to my moves.  I just see if I can understand why the computer recommended move is better than the move that I made.

A blunder is a really bad mistake.

Broadly speaking, in chess, a mistake changes the evaluation of a position, while a blunder changes the result of the game.

To elaborate: If a player, having the advantage, makes a move that loses the advantage but not necessarily the game, he is said to have made a mistake. The same is true if a player in an equal position makes a move that gives his opponent the advantage. A blunder, on the other hand, is a mistake so egregious that it immediately results in an obviously lost position (usually in the form of imminent checkmate, or heavy loss of material such as a major piece). Furthermore, a blunder also has the additional quality of being completely unforced (i.e. not the result of a combination), and not being difficult to avoid; basically the equivalent of a brain fart in chess.

When our opponent makes a miscalculation, it's "a stupid blunder".

When we make a miscalculation, it's "a well-intentioned decision that turned out, in retrospect, to be unequal to meeting the challenge posed by the position".

A mistake (?) turns a drawn position into a lost position or a won position back to a drawn position.
A blunder (??) turns a won position into a lost position.

Mistakes are what u make Blunders are what we make

? ?? ??? ???? ???? ????? ?????? ????????

Play the best move in a position and it’s a ??

One of my moves was from a win to a draw and it was blunder

The definition that tygxc gave is his own definition... that nobody agrees with. Chess.com uses the term differently. Here "blunder" = "big mistake".

As I understand it, a blunder is when a mistake involves some vital piece or position...for example, unnecessarily endangering and losing a pawn is a mistake, doing the same with a rook would be a blunder.