In Jainism, Tirthankaras are not chosen by people or by any authority. They are enlightened souls who appear in the world at times when people need spiritual guidance.

Key points:

• They are those who have achieved full awakening (Kevala Jnana) and have conquered all worldly bondage.
• After their own spiritual purification, they revive and teach the true path, establishing the Jain dharma for the world.
• Their appearance follows the cosmic time cycle. In this cycle, a Tirthankara arises roughly when the collective dharma of humanity wanes and people can benefit most from a proven path to liberation.
• There are 24 Tirthankaras in this half-cycle of time. The first Tirthankar is Rishabhanatha (Adinath) and the last is Mahavira; between them stand the others in a tradition shared by both Digambar and Shwetambar communities. Differences between traditions mainly concern lists and details, not the basic principle that Tirthankaras appear to guide and uplift beings.
• Each Tirthankara also establishes the fourfold order (monks, nuns, laymen, laywomen), builds the Sharavakas/temples, and sets down the Jain code of conduct and philosophy that helps souls progress toward liberation.

If you’d like, I can summarize how each Tirthankara contributed to Jain teachings and list their names in order.