Great way to unwind at the end of the day.
In addition to quests, exploration and various types of battling there is; soccer, racing, demolition derby, mining, cooking and mini-games including tower defense and "bejeweled" types. There is also a wonderful trading card game you can master via free cards and NPC quest series. Some of the later quests are extremely difficult using only free cards. They require you to lose enough times to learn their decks, extra starting cards and strategies then build a special deck (from your collection thus far) to counter it. You can also take your learned skills and well-earned NPC cards to challenge other players or participate in tournaments.
You can play Free Realms for quite some time without spending any money but you must become a member to level any job past level 5. You can level as many jobs as you would like up to level 5 without paying a cent. The membership opens up hundreds of additional quests/levels and goodies and the fee is rather low for a subscription game.
There are other cash dumps built into the game but I have not found a need to purchase any.
The "battles" in Free Realms are not like the high level World of Warcraft battles. If you are looking for that kind of complexity and player interaction you will not be happy with Free Realms. However, battling is such a small part of Free Realms that I would still encourage all hard core gamers to check out free realms for cheery "unwind" time.
I have had the opportunity to experience the winter holidays and holiday goodies in World of Warcraft, Guild Wars and Free Realms. Free Realms was the sweetest to look at, the most fun to play in, and gave away the most goodies and toys with the least amount of effort.
You do not play Free Realms to zerg, participate in epic battles, chase epic loot, and or compete and feel uber. It is not designed for that.
You play Free Realms because it is relaxing and cheerful and contains a large variety of things-to-do and challenges to conquer ranging from very easy to very difficult.