Wut is the difference between cpi and dpi?

Solution
update:
My mistake, i guess you did mean "cpi" but I've not seen it before. I think it stands for "counts per inch" and is the same as DPI?

When it applies to a MOUSE you need one that is good enough for your monitor. There are guides online, then you may need to setup the mouse in the software for it, and if applicable be able to increase or decrease the amount easily by buttons on the mouse (if the cursor moves too slow in a game for example).

Linus did a video: https://www.youtube.com/watch?v=cAEb9a-dltk
update:
My mistake, i guess you did mean "cpi" but I've not seen it before. I think it stands for "counts per inch" and is the same as DPI?

When it applies to a MOUSE you need one that is good enough for your monitor. There are guides online, then you may need to setup the mouse in the software for it, and if applicable be able to increase or decrease the amount easily by buttons on the mouse (if the cursor moves too slow in a game for example).

Linus did a video: https://www.youtube.com/watch?v=cAEb9a-dltk
 
Solution
I have a Logitech mouse, and a 2560x1440 monitor with DPI scaling set to 125%.

I checked my Logitech DPI settings and the DEFAULT one I use after tweaking a bit is 1400dpi. With other games (probably due to different resolution) I use either 800DPI or 2000DPI.

I played also with the POLLING RATE but 125 felt the same as 1000 to me.