A fetch cycle is part of an instruction cycle, and may occur more than once in the cycle.
A fetch is simply the retrieval of an item from memory. Every instruction cycle starts with a fetch, the opcode which the program counter points to. This opcode may be a register bit manipulation or other internal operation in which case that will be the only fetch.
It may also be a move or load, which then executes another fetch from memory to move that value to another location, possibly a register, another memory location or an output port.
The instruction may also be a block transfer in which case many subsequent fetches will be performed on the specified block(s) of memory.