When it comes to religious beliefs, many people have a problem with two terms – christening vs. baptism. It is almost commonly adopted by the society to use those two terms interchangeably. However, not only worshippers have a problem with the differentiation between those terms. Even church representatives tend to use them interchangeably without making proper distinction about two different types.
What is the christening then?
The term “christening” originates from the term “to christen”, which originally meant “to give a name to”, which relates to the religious ceremony of giving the name to a child. When Christian denominations and the whole Christian community are concerned, in the dictionary of religious terms we can find a proper definition of christening as giving a name to a child. Giving a name is strongly rooted into the religious tradition, and during the service of christening, kid obtains a Christian name, and becomes a member of the Church. Tradition of most Christian denominations claims, that a child is properly “introduced” to the God himself.
Christening can be also the part of the whole baptism sacrament and be combined with it during a single ceremony. However, it can also be a single religious ceremony of granting a name, but then it isn't considered a sacrament. It is also important to state, that not every religion baptizes infants, so the christening can take place as a simple religious ceremony of naming a child. Generally, in most denominations christening is the sacrament performed on infants or small children.
When parents aren't of strong religion beliefs, the act of name granting can be carried out in the form of public naming ceremony without any religious connotations.
As for baptism, it is a form of religious ceremony. It is also considered as one of the seven sacraments of Christian Church. It's main purpose is to cleanse the baptised person of the taint of original sin. Considering this fact, the most important moment of the whole ceremony is when the water is poured on the baptised person's head (it really depends on the denomination itself, some religions baptize by submersion or partial immersion in the water). Some Christian denominations baptize children, others baptize adults, and the rest doesn't even consider the service of baptism (like the Army of Salvation). When it comes to Christianity, baptism can be obtained (of course when the denomination considers baptism) at any age.
To sum up, there is a clear-cut boundary between the terms christening vs. baptism. In simplest words, christening is the ceremony of giving one’s a Christian name (or just a name when it comes to non-religious ceremonies), and baptism is one of the sacraments and its main purpose is cleansing the baptized person of original sin.