I'm actually in the middle of re-reading the whole Threefold Lotus Sutra (Sutra of Innumerable Meanings, Sutra of the Lotus Flower of the Wonderful Law, Sutra of Meditation on the Bodhisattva Universal Wisdom) these days, so let's see..
So it looks like what that 5 character thing says is:
During the previous 40 years (According to the Lotus Sutra) Buddha taught certain things to get his followers ready and in the right state of mind, and then at this time he decided that people were ready for the more esoteric deep teachings said to be contained in this Lotus Sutra, so at this point he started teaching about "going all the way", so to speak. He says the previous teachings were a temporary abode for people to aim for and rest in, calling it "nibbana", until they were ready to continue their journey, using a parable about a magical city appearing for some people who were traveling for a long time to stop in then disappearing when they were ready to move on.
(Throughout the whole thing the text refers to many of Gautama Buddha's followers (and the followers of all the other buddhas that appear in this text) as Bodhisattvas, there from the very start, having come to him to hear his discoursing.. That's in contrast to other Vehicles that refer only to certain people as a Bodhisattva, like Buddha himself)
Disclaimer: If I have posted about something, then I obviously have no idea what I am talking about!