Number Systems are simply a way of representing numbers with different symbols. In everyday life we use the base-10/Decimal system to count and complete calculations.
Symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
$324_{10} = (3\times10^2)+(2\times10^1)+(4\times10^0)$
Symbols: 0, 1
$00100100_2 = (0\times2^7)+(0\times2^6)+(1\times2^5)+(0\times2^4)+
(0\times2^3)+(0\times2^2)+(0\times2^1)+(0\times2^0)$
This is equal to 36 in decimal.
This can also be written as 0b00100100
Symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
With A corresponding to 10, B: 11, . . . F: 15
$6B_{16} = (6\times16^1)+(B\times16^0)$
$6B_{16}= (6\times16^1)+(11\times16^0)$