Original: It was a replacement for the Peugeot 309 (which had broken with Peugeot's normal ascending numbering system partly due to it being released before the older and larger Peugeot 305 was axed).
Simplified: The Peugeot 306 is an automobile produced by Peugeot. It replaced the Peugeot 309 in 1993, and in 2001 was replaced by the Peugeot 307.