I've participated in several. What happens depends on the type of retreat. There are charismatic Catholic retreats, retreats based on scriptural themes or daily scripture readings. There's a type of retreat called Cursillos where an overview of the Catholic way of life is given, and community is formed.
Retreats are usually either preached or directed. Preached retreats have a leader(s) who have talks each day, lead prayers and facilitates group discussions. In directed retreats, each person meets with a spiritual director who may suggest scripture passages for prayer and reflection for that person.
In most retreats, there is a lot of quite time for reflection and contemplation. Some encourage keeping a journal. Food is not elaborate and sometimes you sleep on the mats on floors (based on where the retreat is). They are a great chance for spiritual growth. Good luck!
at 9:29 PM on Apr. 5, 2009