Liturgy and Rite
One basic distinction to begin with is Liturgy and Rite. The Universal Church celebrates only one liturgy--the Paschal Mystery of Christ--but does it in a plurality of rites.
Usually, we distinguish between two great families of rites: the Roman Rite and the Eastern Rite (although the distinction is apparently again from a Western perspective). Each ritual family has within it several ritual traditions. One famous example for the Roman Rite family is the Ambrosian Rite.
Before the Counter-Reformation, there has always been a plurality of rites, even when accounting only the Western Church. As a response however to the Reformation, there was a necessity to firmly establish a "Canon" not only for Scripture but for the liturgy as well to safeguard, by upholding the unity of faith and worship, the identity of the Church. The crisis having been addressed, Vatican II opened anew the windows to liturgical inculturation, so that people may celebrate the one worship of the Church, not only preserving the richness of their own culture, but assuming them in the liturgy and enriching both their culture and their worship in the process, making their manner of worship something that communicates intimately to and emanates deeply from their culture, their psyche, their soul (from an Oriental perpective, heart-mind) as a people.
Now, rites are spontaneously and organically formed by a community of people. They are not invented by some scholar or liturgist. Not even the Ambrosian Rite was a mere personal project of Saint Ambrose but a pastoral response to the specific dynamics of his flock.
Scholarship however is able to shed light on what these specific dynamics of a certain people are: how they perceive themselves and understand the universe, what symbols and images speak to them most effectively, in what particular way do they express themselves both in speech and in action. Having knowledge of these data facilitates the spontaneous process of liturgical adaptation, indeed of liturgical inculturation, of forming a rite that is at once universal but profoundly their own. While we do not simply mimic the Roman rite, we also do not hastily incorporate Oriental elements that may not be in conformity with the spirit of the Liturgy. The pastoral task of liturgical inculturation then demands that we be intuitive as well as intelligent, sensitive to the people yet at the same time precise about the deposit of faith, necessarily firm about principles and reasonably liberal about the rest.
Saint Augustine succinctly puts it: In necessariis, unitas; in dubiis, libertas; in omnibus, caritas.