This is different from the Latin rite, but consistent with the various Eastern rites of the Catholic church.
In the Latin rite, confirmation is done at the age of reason; it is consonant with the meaning of the confirmant as becoming a soldier for Christ, capable, for example, to read and understand the scripture.
In the East, both Catholic Eastern Churches and the Orthodox Church, the meaning of chrysmation is the same, but the age is not considered a factor. These are not differences in doctrine, as in either case Christ supplies the soldierly strength on His own schedule.
The difference with the Orthodox is in the understanding of baptism. The Catholic belief is that it remits both the original sin and any personal sin up to the point of baptism, so that a new person, free from the sin of Adam, is born. When an infant is baptized, there is no personal sin, but there is original sin, and that is remitted. In addition, baptism effects the membership in the Church just like the Orthodox say. The difference regarding the original sin is not really a difference in the sacrament of baptism, but rather in the concept of original sin itself. Both agree that concupiscence -- propensity to sin -- is not removed by baptism.
Both also agree that the faith and the will to be baptised are necessary if an adult (or a child past the age of reason, as early as around 7 years of age) gets baptised; when an infant is baptised, the faith and the will of at least one parent is sufficient. The sponsors then take the responsibility to foster the infant in faith.
Of course, any baptism by water in the name of the Father, the Son, and the Holy Ghost is valid in or out of any church. E.g. in an emergency a non-Christian may perform a valid baptism, if he uses water, the Trinitarian formula, and intends the procedure to have the Christian meaning even in absence of his personal understanding of that meaning. Certainly Trinitarian Protestant baptism is valid.
"The difference regarding the original sin is not really a difference in the sacrament of baptism, but rather in the concept of original sin itself. Both agree that concupiscence -- propensity to sin -- is not removed by baptism."
Alex is correct. The sacrament is identical in its essence and efficacy. The actual service is a bit different, for example Orthodoxy baptises by a triple immersion. I will be the godfather at the baptism of an adult on the Saturday of Lazarus. Her baptism will was away all her sins.