Difference between WMTS and WMS?

What is the main difference between a

Web Map Tile Service (WMTS)

and a

Web Map Service (WMS)

When should you choose one over the other?

What are the (dis)advantages by choosing one over the other?

I have read the Wikipedia entries.

Answer

A WMTS delivers tiles (mostly 256x256 pixel size), while WMS delivers one image per request.

Main advantage of tiles is that they can be pre-renderd on the server side, and cached on the client side. This will reduce waiting time for the data and bandwith. On the other hand, you need lots of Gigabytes if you want to pre-render the whole world. Most of it will contain only water.