Theravada… from Pali means “School of the Elder Monks”. I believe it to be the closest existing school to what the Buddha actually taught. Mahayana Buddhism is the other major school of thought and literally means, from Sanskrit, “Major School”. Mahayana tends to concentrate on the path of the Bodhisattva, someone who dedicates their lives to attaining Arahantship then returning in the next life to train and teach others in the Buddhist way, thus delaying their entrance to Nibbana for the sake of other beings.
Theravada Buddhism uses the teachings preserved in the Pali Canon as it’s doctrine and concentrates more on the words of the Buddha. Mahayana has many commentaries on the canon that they follow, which is no bad thing but I find they tend to loose site of the Suttas. But that is just my position. Should you find yourself drawn to the Mahayana form of Buddhism, then please follow it. Truth is in their teachings and any form of truth is better than no truth at all.
Theravada has it’s origins primarily in Sri Lanka, where the Pali Canon was originally committed to writing during the first century BCE. If you wish to read these writings then a major part of them are available on Amazon from Wisdom Publications. I believe the best introduction to the Pali Cannon is an anthology compiled by the Venerable Bhikkhu Bodhi called “In the Buddha’s Words: An Anthology of Discourses from the Pali Cannon.” This work gives a valuable and systematic introduction to the teachings of the Buddha that any beginner will benefit from. I, myself, have a copy and have used this very work to start my journey toward enlightenment.