What is the difference between mov and ldr in arm instructions

ARM is a RISC structure. The movement of data from memory to CPU can only be completed through L/S instructions, that is, ldr/str instructions. 
For example, if you want to read data from somewhere in memory to a register, you can only use ldr 
, such as: 
ldr r0, 0x12345678 
is to store the value at the address 0x12345678 in r0. 
However, mov cannot do this job. mov can only move data between registers, or move immediate values ​​to registers. This is the biggest difference from CISC architecture chips such as x86. 
There is no ldr instruction in x86, because the mov instruction of x86 can move data from memory to registers. 

There is also a ldr pseudo-instruction. Although the ldr pseudo-instruction is very similar to the ARM ldr instruction, the function is not quite the same. The ldr pseudo-instruction can add = before the immediate value to indicate that an address is written to a register, for example: 
ldr r0, =0x12345678 
, so the address 0x12345678 is written to r0. Therefore, the ldr pseudo-instruction is similar to mov. The only difference is that the mov instruction limits the length of the immediate value to 8 bits, that is, it cannot exceed 512. The ldr pseudo-instruction does not have this limitation. If the ldr pseudo-instruction is used and the immediate value following it does not exceed 8 bits, then the ldr pseudo-instruction will be converted to the mov instruction during the actual assembly. 

The ldr pseudo-instruction and the ldr instruction are not the same thing.