If you mean Navpad Oli (also called Ayambil Oli), its significance in Jainism is as follows:

• It is the most important festival of the year, observed twice, for nine days each. The days are devoted to reverence of the Navapad—nine supreme aspects of the universe: Arihant, Siddha, Acharya, Upadhyaya, Sadhu, and the three jewels—Samyak Darshan, Samyak Gyan, Samyak Charitra, along with Samyak Tap. The aim is inner purification and sharpening right faith, knowledge, and conduct. ( jainknowledge.com)
• Ayambil (the daily practice) is a food austerity: eat only once a day, with a plain, minimal, or tasteless meal (no milk, ghee, oil, sugar, etc.), and drink boiled water. The emphasis is on controlling taste to reduce attachment and karmic bondage. ( jainknowledge.com)
• The festival is tied to Siddhachakra/Navapad worship, with liturgical activities such as pratikraman, svadhyaya, and meditation, and it reinforces detachment and disciplined conduct. Digambar and Shwetambar communities may emphasize slightly different liturgical sequences, but the core spirit remains the same. ( jainknowledge.com)

In short: Navpad Oli is a twice-yearly, nine-day sādhanā focusing on the Navapad and Ayambil fasting to purify the mind, strengthen three jewels (faith, knowledge, conduct), and foster self-restraint. For more details, you can read about Shri Navpad Ayambil Oli and its significance here .