According to Shoji Shiba, knowledge has several levels. The first level is simply Exposure. You've heard of Linux, you know what it is, you've had the chance to do some basic stuff with it, like listing the files on the system. It is plain that such a level of knowledge is of very little use.
The second level is Skill. At this level, one's knowledge has reached some usefulness. You know how to ride a bike, and you can use the bike to get you from A to B without much falling down. At this level, your productivity is very basic and inefficient. Workers who are at this level are not very effective. They can do the job but need much supervision to ensure their work is satisfactory.
The third level is Understanding. You have reached the level where you know what you are doing and can make effective decisions.
The fourth, and final level is Mastery. You know how to use the skill at the highest levels and the highest effectiveness that the skill is able to deliver. This is where you are most productive.
It takes time to develop Mastery. It is worth taking the time to study the best ways to shorten the knowledge cycle from Exposure to Mastery.