What is a sacrament in christianity? and explain each one simply.. eg marriage

A sacrament is a Christian rite recognised as of particular importance and significance. There are various views on the existence and meaning of such rites. Many Christians consider the sacraments to be a visible symbol of the reality of God, as well as a means by which God enacts his grace. Many denominations, including the Anglican, Catholic, Lutheran, Methodist and Reformed, hold to the definition of sacrament formulated by Augustine of Hippo: an outward sign of an inward grace that has been instituted by Jesus Christ.[1][2][3][4][5] Sacraments signify God's grace in a way that is outwardly observable to the participant.[5]

A sacrament is a Christian rite recognized as of particular importance and significance. 

And there are 7 sacraments. But here is one of them:

The sacrament of Confession is a regular sacrament we recieve our whole lives where we are always given a chance to repent our sins in everyday life. This is voluntary, as compared to the sacrament of Annointment where a dying person cannot repent anymore for his sins so the priest is the one that does it for him.