Courtship is a vital period in a relationship that precedes engagement and marriage.
since i have never been married, i do not know much about courtship
It's when a couple is getting to know each other to decide if there will be a marriage or engagement. 
that sounds simple, but with important consequences
The average length of a courtship differs greatly throughout the world.
i think some countries take it very serious and is very formal
Yes, in some cases there are arranged marriages where the couple does not get to experience courtship.
yeah, arranged marriages sounds so sad, especially when they are arranged when they are just kids