Your skills should be one of the most important ways in which you gain a reputation within Elysium. For they allow you to carry out tasks which many others cannot, if they have chosen to follow another path with their profession.
Skills range from the art of alchemy, to the dark magics of evocation and the mighty skill of swordplay. Each individual will usually join up with a guild, within which you will learn about the profession which they teach.
The term skill is used to describe the group within which abilities lie. A skill might be demonology, which is the study of demons and their summoning. An ability within demonology might be SUMMON IMP. Note that each skill has many abilities within it, all of a common theme.
By typing SKILLS, you gain a list of all the skills you currently know. To use these skills, you will first need to know what abilities are contained within them. Typing SKILLS <skill name> will give you a list of commands which you can type. Experiment with the abilities you do have, and once you get a taste for more, you should begin asking around for displays of people's abilities and information about the many guilds within Elysium.
Some may be willing to teach you what they know without you needing to join a guild, and so if you wish to learn a skill to get a feel for the most basic of the abilities within it, you should ask someone who has the the abilities within the skill in question.