Mahayana Buddhism reveres the Tripitaka as a sacred text, but adds to it the Sutras, which reflect distinctively Mahayana concepts and are used more often by Mahayana Buddhists.
Most of the Mahayana Sutras, which number over two thousand, were written between 200 BCE and 200 CE, the period in which Mahayana Buddhism developed. Different divisions of Mahayana Buddhism emphasize different Sutras, but some texts, like the Lotus Sutra and Heart Sutra, are important to most branches of Mahayana.
The Lotus Sutra is probably the most significant of the Mahayana Sutras. It describes a sermon delivered by the Buddha to an assembly of buddhas, boddhisatvas, and other celestial beings. This sermon emphasizes the importance of becoming a boddhisatva, realizing one's buddha-nature, and other Mahayana concepts. The Lotus Sutra is revered by most Buddhists, and is the primary focus of the Nichiren school.
The Heart Sutra is another important Mahayana text. It is very short, only a few pages, and provides a concise summary of key Mahayana concepts.
Presented as the teachings the Bodhisattva Avalokiteshvara, the Heart Sutra describes the five skandhas (elements of human nature), as well as the Mahayana views of "emptiness," nirvana, and ultimate reality.
The Land of Bliss Sutra is especially important in Pure Land Buddhism. It tells the story of Amitabha (Amida) Buddha's vow to help people reach nirvana, describes the Pure Land, and relates what one must do to be reborn in the Pure Land.