In general terms, an endowment is a gift. Members of the Church of Jesus Christ of Latter-day Saints (or Mormon Church), however, frequently use the word in connection with their temples, which they consider to be literal Houses of the Lord. In this context an Endowment is a course of teaching, ordinances (sacred rituals), and covenants (mutual promises between the individual and God) received in a Mormon temple by worthy and prepared adult members.
I received my endowment on January 4, 2002. It is a very fond memory for me, especially as I had immediate and extended family present (as well as Elder Jeffrey R. Holland!). I honestly had no clue what was going on, but I felt completely at peace at it all came about. I knew that I would slowly come to understand things each time I returned to make these ordinances as proxy for the dead.
We all hear the same words in the teachings of the Endowment, and we all make the same covenants. But the Endowment is very personal. The thoughts we receive are from the Spirit, and are considered the personal part. They are sacred. They give us guidance and more. I have come to know that there is always something I can learn each time I attend the temple, as long as I have prepared myself and Give my attention to what the Lord wants to teach me. It is a marvelous blessing to have such direct, personal revelation in the House of my Lord.