Big-endian is human friendly. The digits are stored as we(humans) see them.
So, MSB placed at the lowest memory location.
$\begin{matrix} MSB &- &- &- & - &- &- &LSB \\ 0 &1 &2 &3 &4 &5 &6 &7 \end{matrix}$
Little-endian is arithmetic-friendly, and it stores the MSB towards the highest memory location.
If the number is 0x12345678, it is saved as: 78 56 34 12
See the MSB (the digit 1)location here.