If you had to rely exclusively on personal experience to learn everything you needed to know, it would be a long and painful process. In almost every society, there are people who collect knowledge of certain subjects, and pass that knowledge on to those who wish to learn (and are able to pay going rate). It is assumed that most of the things your character knows will have been taught in this manner.
A character who has the Training skill can teach others much more effectively than other characters. This will most often be used by NPCs who are hired to train PCs. The effectiveness of the training depends on the skill levels of both the trainer and the student. If the student's skill level is higher than the trainer's, no training is possible.
To use this skill, first subtract the student's skill level in the skill being improved from the trainer's skill level in the same skill. Multiply the result by the trainer's Training skill level, and divide by 100. The resulting number is the percentage chance that the student will learn something new (ie. the student's skill level will increase by one).
Each attempt at training (successful or not) requires one hour to complete. A successful training session will increase the student's skill level in that skill by one.
The GM will determine how much the training will cost. The cost will be dependent on such factors as availability of trainers, the demand for the trainers available, and the skill of the selected trainer.
Jeanne has a skill level of 28 in Art. She wishes to increase this, so she signs up for a night course at a local college. The course is two hours a night, one night a week, for a month, so there are a total of eight hours in the course. The teacher has a skill level of 76 in Art and 84 in Training. The first hour, the difference in skill levels is 48(=76-28), so Jeanne has a 40%(=48*84/100) chance of learning something. She rolls a 36, so her skill level increases to 29. The difference in skill levels in now 47(=76-29), so her chance of learning in the second hour decreases to 39%(=47*84/100).