The Settlers Online is an online browser-based resource-gathering, city-managing and empire-building game which is based on the original 1993 The Settlers game. It is published and by Ubisoft and maintained by Blue Byte Studios, the original The Settlers developers. It takes place in a medieval world where you became mayor of a small, underdeveloped and uninhabited settlement. Your goal is to construct buildings, satisfy your people's needs and grow your small village into a large, bustling town.
The game itself is very similar to any other empire-management RTS out there. You order your villagers and workers to gather resources and process them, give orders to build and repair, and build armies and send them to explore and conquer other settlements. Similarly to other persistent online RTS games, everything is time-gated, which can be sped up by purchasing Gems with real money. There is no PvP in this game as of now, so you cannot be robbed by other players.
The game may start out very fast at first, but soon your construction times and army movements will shoot up from minutes to the hours. Also, due to it being an online game, it requires you to add other players to your friends list and ask them to buff your quests. This game has a very active and friendly community, so don't be afraid to ask for help in the Help channel.