Analysis: What's Up With the Title?
Let's take this in parts and, just for kicks, we'll even go backwards. Terabithia is the magical, imaginary land invented by the book's two main characters, Leslie and Jess. It's a part of a forest and they have to cross a creek by swinging on a rope to get to it. But, once they make it there, Leslie and Jess aren't just out-of-place fifth graders – they're a queen and king.
The "bridge" part of the title is both literal and metaphorical. At the end of the book, Jess literally builds a bridge to Terabithia that crosses the creek (see "What's Up With the Ending?" for more on this). It's an actual object that connects imaginative Terabithia to ordinary Lark Creek. But, the idea of the bridge can also be seen metaphorically, as something that connects Jess and Leslie, that solidifies their friendship, and that links them to that magical place, Terabithia.