Tiantai is a school of Buddhism that originated in China during the 6th century and is based on the Lotus Sutra. This school emphasizes the idea of integration, or harmonizing, all Buddhist teachings around the Lotus Sutra. This concept is known as the "One Vehicle" or "One Buddha Vehicle" doctrine.

In terms of its relationship with other forms of Buddhism, Tiantai shares some common elements with Zen and Pure Land traditions, while also having distinct differences.

Firstly, Tiantai and Zen both have a strong focus on meditation and the realization of ultimate truth or enlightenment. However, Tiantai places more emphasis on the use of different meditation techniques, such as concentration and visualization, while Zen emphasizes the practice of sitting meditation (zazen).

Secondly, Tiantai and Pure Land both have a strong devotional aspect, but with different focuses. Tiantai emphasizes the importance of devotion to the Lotus Sutra and its teachings, while Pure Land focuses on devotion to Amitabha Buddha and the practice of reciting his name for rebirth in the Pure Land.

Despite these differences, Tiantai, Zen, and Pure Land all share the common goal of achieving enlightenment and ending suffering. They also all recognize the importance of understanding and studying Buddhist teachings, rather than blindly following rituals or beliefs.

Furthermore, Tiantai, Zen, and Pure Land all have a strong emphasis on the concept of emptiness, or the idea that all phenomena are ultimately empty of inherent existence. This concept is crucial in understanding the interconnectedness of all things and the true nature of reality.

Overall, while Tiantai has its own unique teachings and practices, it also shares many common elements with other forms of Buddhism. This highlights the idea of integration and the unity of all Buddhist teachings, which is a central concept in Tiantai Buddhism. By recognizing and embracing these similarities and differences, practitioners of Tiantai, Zen, and Pure Land can deepen their understanding and practice of Buddhism as a whole.