"THE liturgy" in Orthodox parlance refers to the Divine Liturgy, ie, the service which culminates in Holy Communion.
Liturgy is any rubric for worship. Liturgical worship is just a way to describe something that follows a rubric, though as poster above me pointed out, all denominations have some kind of form they follow.
So, liturgical services in orthodoxy are usually called the divine services and include vespers, orthros (matins) etc.
As far as lent goes... the resurrection was the first holiday of the church and remains the focal point of our entire year. Every week is a microcosm of the annual calendar. Every Wednesday we fast in memory of His betrayal, every Friday we fast and mourn His death, every Saturday is His rest, and every Sunday we celebrate His resurrection. For this reason we don't kneel or prostrate Sundays, because on Sundays we are reminded that we are become sons of God.
In the ancient church people prepared for baptism on Pascha by prayer and fasting, and the faithful joined with them. Numerous ancient texts such as The Didache, the writings of St Justin and St Hippolytus reference to the practice of fasting with those to be baptized. Lent is an outgrowth of this, it's us preparing for the great Passover, because He is our Passover.
For orthodox the Lenten services are in the Lenten Triodion, named for the style of the verses in triads. This service book has all of the hymns, prayers, etc said in all of the divine services starting ten weeks before Pascha and ending with the service of Pascha.
Aside from the actual words of the prayers the main differences during lent are ceremonial things and new or different services. We use different lighting, the church actually stays quite a bit darker during lent (just as we use different lighting in vespers vs orthros vs liturgy). Because the overall spirit of lent is one of anticipation and not celebration, we don't celebrate the liturgy except on sundays, and instead during Sunday we reserve a portion of the gifts for use in a presanctified Liturgy service.
We have other special services that involve readings as the canon of st Andrew or the life of St Mary of Egypt.
http://www.orthodox.net/greatlent/great-canon-of-andrew-of-crete-explanation.htmlAlso, the services before great lent are all of comparison for us, one good example, one bad. (Pharisee and publican, prodigal son, sheeps and goats). The Sunday before the beginning is the Sunday of forgiveness, and lent begins with a service called forgiveness vespers, so we can enter into the fast with a clear conscience.
We add the prayer of St Ephraim to our morning and evening prayers.
https://en.m.wikipedia.org/wiki/Prayer_of_Saint_EphremAnd of course... we fast.
The traditional fasting discipline begins with the Sunday of the publican and Pharisee. The following week we do not fast at all, to remind us to not be like the Pharisee. The following Sunday is meatfare Sunday, and is the last day of meat. The final week before is fast free except for the absence of meat, to clean out eggs, cheese, etc.
Traditionally we fast from all animal products, olive oil, and wine. Animal products includes dairy and eggs, and meat (the exception being shellfish - basically poor people food an antiquity). Olive oil usually covers fried foods as well. Wine is usually interpreted for all liquor. But beer is always ok.
The first three days of lent are typically a "black fast" - no food at all, and we break our fast Wednesday night (tonight) after the first presanctified service. Many people will take a small meal, or uncooked food only as no food for three days is pretty tough.
We eat fish for the feast of Annunciation (3/25) and on the feast of Palm Sunday. And wine and olive oil are eaten on weekends.
Fasting is a long discussion that I'll save later, but it's important we don't become pharisaical about it. The spirit is what matters.
Great Lent ends on Lazarus Saturday, the day before Palm Sunday. Holy Week is technically separate. The Holy Week services we have today are not particularly ancient, but they are quite beautiful.
You can read about them here
http://www.antiochian.org/1175027131Summary is:
Monday - commemoration of st Joseph the son of Jacob (as a type of Christ) and parable of the fig tree
Tuesday - parable of the ten virgins
Wednesday - sinful woman who anointed Christ and the service of Holy Unction
Thursday - twelve readings from the gospels about the passion
Friday - no liturgy of any kind. Black fast day. Unnailing vespers and lamentation service - first glimmer of joy
Saturday - my favorite day of the year. Hope and barely restrained joy. Priests wear white, Liturgy in the morning where we celebrate victory over death. We read about Jonah and the whale and sing arise O god and judge the earth (Ps 82:8).
Saturday night - Pascha service begins late and ends in the wee hours of Sunday morning. Then you bless the food and feast!! Bright week is the week after, fast free, all light and joy.
Man I get chills just thinking about it!!!