Cities are major settlements that holds important services and places for the travelers. They have depots, where you can store whatever you find on your adventures, weaponry and armory shops, where you can buy and sell equipment pieces, bank to store your cash and other minor services.
You can set and change your hometown in one of those cities whenever you want to, so it becomes the city you appear when you die. All of them offers ship services as transport method, so you can go to the linked cities on a fast and cheap way.
You can also rent houses or rent guildhouses if you are the leader of a guild. For a small share of your gold pieces, you can have your own headquarter, a nice place to sleep and to show all your wealthy to another adventurers.