A [testimony] consists of beliefs and convictions regarding the truth of the Gospel. Members of The Church of Jesus Christ of Latter-day Saints are encouraged to "bear" their testimony, or, in other words, share their testimony, with others. There are frequent opportunities for members to bear their testimonies with friends, family, and others. One common opportunity is Fast and Testimony Meeting, which is a meeting particularly dedicated to bearing testimonies and is usually the Sacrament Meeting held on the first Sunday of every month.
The following is a video clip from the 178th General Conference of the Church, held in April, 2008. It includes testimonies from the Quorum of the 12 Apostles: