This section is an overview of Fortifications.  Sometimes, in the forums, Fortifications are referred to as Forts, and thereby easily confused with Fortresses.  Fortifications and Fortresses have nothing to do with each other. 

Fortifications are a key facet of the game.  Like many of the LandGrab features, there are different options that can be turned on based on the wishes of the game creator.  Be sure you are aware of what your fortifications rules are for each game you play.  They are summarized in the options section of the Games Page.  The options section will look something like this (depending on whether or not you are in a team game):

Look at the right side: see "Fortifications: 1 path".  This tells you that for this game you get one Fortification, and it must be made along a path of owned territories.  The options for Fortifications are as follows:

1. Path - this is the most common. This means that you can fortify from any territory that you own to another as long as there is an owned path between them. In other words as long as your troops can travel from one point to another by only going through territories that you own.
2. Border - with border forts, you can only fortify from one adjacent territory to another. This makes planning for attacks more complicated as you may not be able to use your forts to cover your chokes, unless you really plan well. Thankfully this is not used very commonly.
3. Any - with this setting you can fort from any territory to any other territory that you own. it doesn't matter where the other territory is.

Fortifications are very important strategically to your game. When planning your attacks make sure you have enough fortifications to cover your newly conquered lands. You don't want to take a continent with 3 chokes, but due to poor planning and only one fortification find that you can only cover 2.