Bits in memory have no meaning. It is up to the computer program to know if the bits are an instruction, string, number etc.
How does the computer know? In the case of compiled programs it knows because the compiler knows what the compiler(or linker) stored where in memory, we can still goof and use data of the wrong type. If we are lucky the compiler will catch it. In the case of asm it is up to the programmer(human) to ensure that he understands what he has stored at each memory location.