If you plan on engaging in combat, either against non-player characters in the world, or against players in the wilderness, you will want to make sure that you have equipment with good offensive and defensive bonuses.
There are several different levels of equipment in RuneScape; from the cheapest, easiest to wear sets that offer very small defensive bonuses, to the more expensive sets that cost a lot of gold, and require high skills, but offer great benefits to your character. When you buy a set of armor, you get a note, instead of the individual items. You can redeem this note by speaking to a banker.
The main types are listed as follows: