They built castles for comfort from the elements and to provide a safe haven in
times of war!
How?
In earlier centuries castles were built out of wood, dirt and were simple in design.
As castle building evolved so did design and building materials. As the centuries
grew on castles were built out of stone and became bigger and stronger.
Why?
Medieval lords built castles for themselves, families, staff and to provide a secure
haven in a time of need e.g. a seige\attack by an enemy.
They eventually became large enough to hold an entire small community in a war.
To Build a castle you needed:
Permission from your King in order to get the land
To be sworn in by your King as owner of land
If you were a King you could build anywhere without permission within country!