Other forms: coming full circle; came full circle; comes full circle
The phrase come full circle is often used in the context of completing some kind of cycle. Think of it as a metaphorical racing track, with the start and end being the same point.
An example of coming full circle is the hero or heroine of a book who goes on many adventures, learns new things, defeats a great evil, and then comes home to their family. Although they're back where they started, the feeling of being in that place is no longer the same, because they are not the same. When you come full circle, you're back in a place you've already been, but with a different context for it.