In order to understand how IP addressing works you need to understand binary mathematics.  Computers and networking equipment do not understand decimal.  We use decimal because it is a numbering system using ten digits, it was invented by a caveman centuries ago when he realised we all had ten digits on our hands and they could be used for counting dinosaurs as they walked past his cave.

Computers and networking equipment can only understand electrical signals.  Since an electrical signal can only be on or off the only numbering system that will work is binary.  Binary only uses two numbers, a 0 or a 1.  A 0 means there is no electrical pulse on the wire and a 1 means that there is a pulse on the wire.

Any number can be made up from binary values.  The more binary values we add the larger the number can become.  For every binary value we add we double the next number i.e. 1 to 2 to 4 to 8 to 16 and so on into infinity if we wished but we start at the right and move left.  With two binary digits we can count up to 3.  We just place a 0 or a 1 in the column to decide if we want to use that value or not.

We will start with only two binary values in the columns, 1 and 2.