The Triple Gem, also known as the Three Treasures or Three Jewels, are primary objects of devotion in Buddhism. Depending on the tradition the Gem is defined differently. I will define them for my practice.
- Buddha - the historical Buddha known as Siddhārtha Gautama or Sakyamuni. Buddha wasn't a Buddhist any more than Christ was a Christian. According to the stories, Buddha was a prince who left his royal palace in search of something better. His search ended when he obtained enlightenment at the age of 35 under the bodhi tree. It was at this time that he realized the 4 Noble Truths. Anyone can obtain enlightenment in this lifetime. Buddha means Enlightened One. We all have the Buddha inside of us. The 1st Gem refers to the historical Buddha as well as our Buddha nature.
- Dharma - teachings. Buddha's teachings are found in the various sutras. Different traditions place emphasis on different sutras. I think that good can be found in all of them. I would include in dharma commentary written on the sutras. However, like Buddha said, take what you find useful and throw the rest away.
- Sangha - community of Buddhist practitioners, Some sects only include members of their own sects as the sangha. Practitioners who use technology like Online Meditation Crew (#OMCru) have a twangha (Twitter + sangha) where everyone is welcome. I like the all-inclusive definition better.
My practice does not require me to take refuge in the Triple Gem. I suppose this is sort of like a Buddhist dedication. At any rate, the Triple Gem is a good foundation for any Buddhist practice.