You know how some languages write left-to-right, and some rught-to-left? Endianness is that, for numbers.

Or another analogy is dates: 2025/12/31 is big endian, 31/12/2025 is little endian. And 12/31/2025 is middle endian. Which makes no sense at all because the middle is, by definition, not an end.

Big Endian    Little Endian:
 
 "1010"         "1010"
  ||||           ||||
 [1248]         [8421]
 
 1+4=5          8+2=10

Depending on whether the order of binary comes from the left (Big Endian) or from the right (Little Endian), the binary number of "1010" can equal 5 or 10

Ouch. I had to learn endianness once to solve a real life serialization bug. It sucked. I learned it for just long enough to correct the code for the corner cases involves, and then slept and forgot everything about it.