Communion on the tongue refers to the practice of receiving the Eucharist by placing the consecrated host directly onto the tongue by the priest, rather than into the hands of the communicant. This is the standard, traditional practice of the Catholic Church. Communion in the hands is an innovation that brings disrespect to the Body of Christ.
The decision to receive communion on the tongue or in the hands is not a personal one, and it is not up to the individual to decide which method he or she prefers.
Communion on the tongue is required unless there is a very serious reason to offer it in some other manner.