Skills are learned by practicing or studying. Each skill is typically grouped in a larger category (such as 'physical' or 'knowledge'). Increasing a skill confers some benefits to your character, such as being able to complete a task faster or more accurately.
If your character has a skill that is no longer used, you may find it helpful to use the 'updateskills' command. Your skills will be updated immediately.
The list of unused skills and their revisions follows:
fire making wilderness lore
basket weaving weaving
embroidery sewing
spinning weaving
coopering carpentry
shipwrighting carpentry
pastry creation cooking
baking cooking
underdark lore underworld lore
milling sewing
find traps perception
first aid lore first aid
tending first aid
glass blowing glass working
glass making glass working
small shield shield
round shield shield
tower shield shield
spiked shield shield
mining lore geology
chain whip
cobblery leather working
See also: skill messages, skill, levels