actually, they're very similar in the sense they both can mean "what". but each is used based on the context.
In current colloquial arabic, majority use ايش or شنو or ايه or شو for "what". very rarely you'd hear ماذا.
ما has other meanings, more commonly nowadays as to negate sentences. in some cases you'll only tell the difference by context, if it's written in formal arabic or colloquial. e.g., ما قرأت
it can mean:
1. I haven't read. (in colloquial).
2. What I've read. (in formal fus-ha)