The little el-cheapo OBD II scanners can clear codes, and they can also tell you any codes that are stored, even ones that aren’t currently generating a CEL. They also generally will tell you some real-time running information. If you reset the data and the ECU hasn’t had enough time or different conditions or whatever for the data to be valid, the cheapie OBD II scanners can tell you that, too.
And that’s about it.
The fancier ones will give you more information and can access and interpret some data that the el-cheapo OBD II scanners can’t. They might even be able to initiate certain diagnostic tests and write some types of data to tune the engine’s performance. The el-cheapo ones usually can’t write anything, other than clearing the codes.