Travian is a Massivley Multiplayer Online Game (MMOG) which is played entirely through your web browser. Any 4th generation browser or higher is sufficient.

The idea is to grow your village by harvesting resources such as wood and crops and build your armies to defend or attack othe villages.

If you are familiar with Settlers then you will understand how it is played.

Although the game is free there is a 'plus' version which gives you a few more things. It is not a lot of money, from $2.99 a month and if you play the game a lot it would be worth paying out to keep the game going. As of writing there are currently over 16,000 active players.