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.