Why can i play the shaders mod on minecraft?

Your PC probably can't run it. You need a high end PC to run shaders mod. Get a better PC then try again or just don't install the mod.

I wouldn't recommend shaders unless you have a really good performing computer. Shaders takes A LOT of fps and with a slower computer you'll freeze, get lag spikes, etc.

Some shader packs are "broken" as unzipping them either corrupts the file or something is overwritten.