There are two common Jain meanings for “Purva” (singular Purva):

• Purva as a time unit: In Jain cosmology, one purva is a very long span of time. It is described as 84,00,000 purvāṅga, and one purvāṅga equals 84,00,000 years, so one purva is an enormous, symbolic timespan. This usage is about measuring ages of Tirthankaras and events in cosmic time. You can read more here .

• Purva as a class of ancient scriptures: Purvas are the oldest Jain texts that predate the later Angas. There were traditionally 14 Purvas, said to be lost long ago but once regarded as the foundational, extremely ancient teachings of the Jinas. Both Śvetāmbara and Digambara traditions acknowledge their existence and loss, with later texts referencing their ideas. You can read more here .

If you meant one of these specifically, tell me which sense you’re after and I can give a brief, precise summary in simple terms.