if we assume address 0x100 is start of program and from 0x100 to 0x103 is instruction mov ax,5

so in memory 5 as 16-bit register is stored in 2 bytes 0x100 and 0x101 it should be stored as 00 in 0x100 and 05 in 0x101 but in little endian it is stored as 05 in 0x100 and 00 in 0x101 the reason that the least significant bit is stored in lowest address i.e. 05 in 0x100 and 00 in 0x100

to understand in detail check my medium blog about this https://medium.com/@farhanalam0407/high-big-endian-and-low-small-endian-a365a724dd0c