Instruction dispatch involves fetching/reading an instruction from memory, and jumping to the corresponding segment of code that implements the instruction.
In a stack based architecture an addition would look like:
I1: LOAD C
I2: LOAD B
I3: ADD
I4: STORE A
You fetch the values from the stack and push the result back on it (hence the name stack based architecture).
In a register based architecture:
I1 "ADD, a, b, c"
a,b,c being registers.
A register based architecture does not completely avoid fetching instructions but it reduces the number of them.