The terms tall ship that we will use often in this site does not correspond to a specific type of sailing vessel. It usually means a large, traditionally rigged (in terms of sails) sailing vessel. It can be “technically” a full ship but doesn’t need to be.
The biggest type is called a full-rigged ship and it looks like this:
A full-rigged ship has at least three masts all square rigged (her name is Christian Radich)