In the simplest terms, vocation means a call. So, in general terms, a vocation is what God calls us to do with our life.
Everybody is called by God to know, love and serve him. The difference is how each one does this. Individual vocations vary between being single, married, consecrated, religious or holy orders, such as priest or deacon. However, we usually use vocation to mean a call to the consecrated, religious or holy orders.
In the one life God gives us to live, we have one overriding purpose, to fulfill the will of God, because this is the key to our true destiny, eternal happiness. God gives each one of us a particular mission in life. As we grow and life progresses, he makes it known to us, usually in indirect ways, more as an invitation than an imposition.
Discovering and ultimately following our vocation gives the greatest glory and praise to our Creator. It is what we were meant to do. “Take up your cross and follow me” (Mark 8:34). Remember, God does not call the qualified, but rather qualifies the called. (8:49)