CPU Bound means the rate at which process progresses is limited by the speed of the CPU. Example: Machine Learning training algorithm, Image Processing, Hashing, Encrypt/Decrypt, ....

I/O Bound means the rate at which a process progresses is limited by the speed of the I/O subsystem. Basically, I/O bound tasks will working with kernel APIs and waiting for response as result of kernel process. Example: Files Processing (Read/Write), Database Query, Network call....

Memory bound means the rate at which a process progresses is limited by the amount memory available and the speed of that memory access. A task that processes large amounts of in memory data, Example: multiplying large matrices, Memcache Database.

Cache bound means the rate at which a process progress is limited by the amount and speed of the cache available. A task that simply processes more data than fits in the cache will be cache bound.