What's the difference between 3D tiles and 3D model?

I’m new to Cesium.I noticed there are 3D-Tiles and 3D-Models in the tutorials.The 3D-Tiles actually use the gltf format,same as 3D-Model.So what’s the difference between them?

A 3D model is what it sounds like, a model with vertices, faces, perhaps materials and animation.

3D Tiles is a format for breaking up 3D data into chunks so that it can be streamed. Imagine you have a huge 3D model that would be inefficient to render/load all at once, so if you convert it into the 3D Tiles format then the Cesium viewer can load only the necessary bits. You can make 3D tiles out of traditional 3D models, point clouds, both or more. You can read more about it here:

I hope this helped!

Also, just to clarify, some types of 3D Tiles formats, like Batched 3D Model and Instanced 3D Model, embed binary glTF with additional metadata to form a tile, and then these tiles are organized into a tree forming a tileset.