Ok I tried to search for answers to these questions here and elsewhere but I'm still confused. First of all, is there a difference between 1/8'' and 3.5mm? If so, I'm guessing mini refers to 1/8"? Also, is there any appreciable difference between any of the sizes in sound quality(1/4" vs 1/8" vs weird metric measurements)?

Lastly I have a super weird thing I found out playing with some adapters I had in a box with other random stuff. I found an adapter that seems to be an 1/8" male to 1/8" female. I could only assume it was just an extention or something even though I have no idea why anyone would need that. Then I tried to use it between an 1/8" headphone plug and an 1/8" jack. Headphones worked the same as always.

This is the weird part.

I found that if I used a mini splitter, and pluged the adapter into one of the split jacks and my headphones into the other, both the left and right channels went to my left ear (of the side of the splitter without the mystery adapter. Which I'm glad I found cause I was looking for a way to listen with one ear but still have both channels present. (Checked it with left/right EQ) (And if anyone has any other advice on how to do that (condense both channels into one side of a set of earbuds) I'd be appreciative too) If I plug another headphone into the mystery adapter that headphone works normally but the mono thing is still present on the other headphone.

So anyone have any clue what the hell this mystery adapter is and how it could do that?

I am so confused...

A stereo to mono adaptor.