Basic skills, meaning those it is a shame to battle without.

Dodge

The overall ability not to get hit, a very useful skill indeed. When your foe tries to hurt you, you, as the defender, try to dodge the blow. Should you succeed - the attack misses. The chance of succesfully avoiding hits grows as you hone the dodge skill, as well as it depends to some extend on your in-game luck (which is the principal attribute of humans), and the luck and melee skills of the opponent (plus eventual bonuses of his weapon).
The dodging skill grows everytime the opponent misses you in battle AND when he succesfuly strikes, yet much less in the second case.

Magic

It's the skill that lets you cast magic spells. It describes how good you are as a magician and how easy (or hard) it is for you to cast spells. The skill is also important while buying spells, because all incantations have a minimum Magic skill requirement that needs to be fulfilled of course. The higher skill you have the more probability is there to successfully cast a spell. Additionally, rasing that skill enhances your magical damage dealt. Efficiency of casting a spell depends on your Magic skill, luck, your profession (adepts of magical arts have it easier than fighters) and difficulty of the spell itself.
Your skill improves a bit whenever you successfully cast a spell (either defensive or offensive), so the more spells we cast the faster the skill increases.
Everybody who is eager to cast spells can try it; however, for some it will be quite easy, for others less, and the final effect may also be pretty different...

Sword

Fighting your way with the sword. This skill is utilized while fighting using all kinds of swords. It's crucial during a melee combat. The skill is needed to wield a sword precisely and efficiently; it means to hit a foe even though he doesn't want to be struck. A successful hit is a sum of sword skill, luck, weapon bonuses, race (and attributes like dexterity) and how well the opponent mastered the dodging (see dodge skill above).
The skill rises whenever you hit an opponent. However, even if you miss him you might learn something too.

Mace

It's stunning with a mace or a morningstar. It works in the same way as Sword skill, except it applies to all kinds of clubs, maces, morningstars and hammers.

Axe

Axe-wielding. Similar to the sword skill, only this one applies to using axes.

Staff

Stick-bashing. Just like with any other arms (swords, axes or maces), this skill is used when fighting with a staff. Staves are most worthwile for an Adept or someone of the more powerful mage professions, as many better staves can increase the magic abilities (the magic skill) of the wielder.

Bow

Shooting from the distance; the ability to use the long-distance weapon - bow
This skill is needed to hit the enemy with your arrow, before he will reach us with his sword. But first you need to have a long-distance weapon to be able to sting somebody with it just before the fight. When this condition is fulfilled, you also need to hit the enemy, and to do that you need not only luck, but also some experience in using such weapon (which means that the higher your distance skill is, the higher chance of hitting the target you have). What is more, chances of hitting the target are enhanced by the shooting weapons themselves. It is much easier to hit the target with a crossbow than a bow. Moreover, when we hit somebody with the crossbow he'll writhe with pain and desperation.
However, a bow is much faster than a crossbow and enables you to use it more times than the latter.
The skill rises when missile will reache the target.

Crossbow

Shooting from the distance; the ability to use the long-distance weapon - crossbow. The same as Bow, but for crossbow.

Parry

Parrying a blow with a weapon, saving your life. Take two gentlemen fighting with swords for instance, and one charges an attack... then the other one may parry it, making his sword receive it, without taking a scratch himself. The better you are in this ability (meaning LUCK + parry skill) the more probable you will succeed in parrying... and avoid being hit of course. It goes without saying that the more skillful is your adversary in attacking, the harder it is for you to parry his attack. Additionally, you will be less likely to do it, when your foe is from the stronger sort.
Some weapons raise the chance to parry a blow with their very shape - it is easiest to parry with a sword, and a lot harder with an axe.
This skill rises every time you successfully parry an attack.