Mages
Mages use runes to cast spells. Runes can be made using the Runecrafting skill. There are a variety of runes, each having its unique purpose. The elemental runes include Air, Mind, Water, Earth and Fire. Free-to-Play players can make and use all the elemental runes, including the Body rune. They can also use Cosmic, Chaos.
You may also use staffs that can be wielded and provide and unlimited supply of the staff's rune. Mages are very expensive to maintain, but can hit very high depending on the spell you are using and your magic level. Mages have the advantage of being able to hit from afar, thus taking no damage when dealing with warriors.
Rangers
Rangers are my personal favorite class. They use arrows from bronze to dragon to use with their bows. Members can make bows and arrows. To make a bow, cut down a tree and fletch it into either a long bow or short bow. Your woodcutting determines which kind of trees you can cut down and your fletching determines which kind of logs you can fletch. Members can make up to magic bows, there are also crystal and dragon bows but those cannot be made. Free-to-Play players can only use up to maple bows and wield up to adamant arrows.
Rangers, like mages, can shoot from a far without taking damage. They shoot moderately fast and have the option to shoot in “accurate” or “rapid” mode. Accurate mode shoots slower than rapid mode, but hits higher. Rapid mode shoots faster than accurate mode, but doesn't hit very high. Rapid mode usually evens out the hits when using any bow except crystal. I personally only use accurate mode when power training. (Power training is when you don't pick up your arrows after you shoot them.)
Warriors
Warriors use many different types of weapons from a dagger to a 2-hander. Also, weapons can be made of bronze up until rune. Both Free-to-Play players and Members are able to make weapons up to rune. Some weapons, such as dragon, cannot be player made. Different types of weapons have their advantages and disadvantages. For example, the scimitar hits much faster than the 2-hander, but the 2-hander can hit exceedingly higher than the scimitar.
Although the warrior can hit very high, it has to fight in close combat. All the warrior's weapons, except for the halberd, can only be used in close combat where your opponent can hit you back. To prevent major damage, warriors have the ability to use armor. Armors can be made of bronze up to rune. Some armor, such as dragon, cannot be player made. Armor can be costly, but armor can be used for an unlimited amount of time, except barrows. So, armor is a one time cost, unless you die.
Final Notes
Remember, when fighting against another class the combat triangle is vital. Mages beat Warriors, Warriors beat Rangers, and Rangers beat Mages.