All Christians are called to a vocation -- God's unique plan for each person to draw them to Himself, who is love. For most, their vocation is to marry.  Others are called to be a deacon or to the single life as a layperson, priest, brother, or nun.  At the heart of all true vocations is the call to love - this is beautifully expressed in Pope John Paul's, "Familiaris Consortio" - On the role of the Christian Family in the modern world.

"God created man in His own image and likeness : calling him to existence through love, He called him at the same time for love.  God is love and in Himself He lives a mystery of personal loving communion.  Creating the human race in His own image and continually keeping it in being, God inscribed in the humanity of man and woman the vocation, and thus the capacity and responsibility, of love and communion.  Love is therefore the fundamental and innate vocation of every human being." (Familiaris Consortio, paragraph 11)

The sub-categories above contain some further information and guidance on vocations.