If you ask who they are, you will be told that they are the Enlightened One's two Chief Disciples, the Arahats Shariputra and Maha Moggallana. They stand in the positions they occupied in life. Shariputra on the Buddha's right, Maha Moggallana on his left. When the great stupa at Sanchi was opened up in the middle of the last century, the relic chamber was found to contain two stone receptacles; the one to the north held the body relics of Maha Moggallana, while that on the south enclosed those of Shariputra.
http://www.buddhistinformation.com/life_of_shariputra.htm
1. Shariputra
http://en.wikipedia.org/wiki/Sariputra
Sariputra (Sanskrit) or Sariputta (Pali) was one of two principal disciples of the Buddha. He became an Arhat renowned for his wisdom and is depicted in the Theravada tradition as one of the most important disciples of the Buddha. Sariputra came from a Brahmin family and had already embarked on life as a spiritual ascetic when he encountered the teachings of the Buddha. Shariputra had a close friend Mahamaudgalyayana (Pali: Mahāmoggallāna), another wandering ascetic. They both renounced the world on the same day and became disciples of the skeptic philosopher Sanjaya Belatthiputta before converting to Buddhism.
While depictions of Shariputra in the Pali Canon are uniformly positive, showing Sariputra as a wise and powerful arhat, second only to the Buddha, his depiction in Mahayana sources has often been much less flattering. In the Vimalakirtinirdesa-sutra and the Lotus Sutra, Shariputra is depicted as the voice of the Hinayana or shravaka tradition, which is presented in Mahayana sutras as a 'less sophisticated' teaching. In these sutras, Shariputra is unable to readily grasp the Mahayana doctrines presented by Vimalakirti and others, and is rebuked or defeated in debate by a number of interlocutors, including a female deity who frustrates Shariputra’s 'Hinayana' assumptions regarding gender and form.
2. Maudgalyayana
Maudgalyayana (Pali: Moggallāna), also known as Mahamaudgalyayana or Mahamoggallāna, was one of the Buddha Shakyamuni's closest disciples. A contemporary of famous arhats such as Subhuti, Shariputra, and Mahakasyapa, he is considered the second of the two foremost disciples of the Buddha, together with Shariputra.
Maudgalyayana was most accomplished of all the Buddha's disciples in various supernatural powers. These abilities included being able to use mind-reading for such things as detecting lies from truths, transporting himself from his body into the various realms of existence, speaking with ghosts and gods. He was also able to do things like walking through walls, walking on water, flying through the air, and moving with a speed comparable to the speed of light.
3. Ananda, Skt. “Bliss”
Ananda was the first cousin of the Buddha, and was devoted to him. In the twentieth year of the Buddha's ministry, he became his personal attendant, accompanying him on most of his wanderings and taking the part of interlocutor in many of the recorded dialogue.
Because he attended the Buddha personally and often traveled with him, Ananda overheard and memorized many of the discourses the Buddha delivered to various audiences. Therefore, he is often called the disciple of the Buddha who "heard much". At the First Buddhist Council, convened shortly after the Buddha died, Ananda was called upon to recite many of the discourses that later became the Sutta Pitaka of the Pali Canon.
