INTEL x86 instructions: why movl/addl/etc instead of mov/add

I am new to INTEL architecture (know about ARM architecture), By looking into the assembly instructions for INTEL x86 I've observed that 'l' is almost appended to all the instructions e.g movl is used instead of mov. Does the instruction try to access lower 2 bytes, if that is the case why don't utilize whole 4 bytes ?