In order to learn, the human brain is forced to translate a lot of observations. At its most basic level of operation, the brain manages knowledge as associations, such as associating sharp teeth with danger. It does this in order to find an appropriate reaction to its environment, building mostly on experience, either having been forced to react in such a manner (having experienced pain from being bitten) or imitating the reactions of others (having seen mom express fear of sharp teeth. Irrational fears, such as arachnophobia or fear of mice are often inherited this way, a child witnessing an adult being afraid of spiders or mice).

This level of instinctive reaction is one of the lowest cognitive levels; the brain can immediately associate an input with a proper reaction ('proper' according to its own experience, anyway).

A slightly higher cognitive level can be seen in spoken language. Most people, when hearing the word explosion, will instantly think of an explosion either seen on TV or in real life. From that, they will associate it to a lot of other things, perhaps danger, perhaps excitement. Some associate to things that make no sense to others, possibly not even to themselves. The point is, language needs some translation in the brain in order for the brain to know what to do with it. Granted, most operate just fine without worrying about this in day-to-day life; the brain does most such translation subconsciously. However, it still takes a mental effort.

Jumping a bit higher in cognitive levels, we reach text, or other symbolic languages. These (usually) need to first be translated to spoken language (even if you do not move your lips, you will sometimes notice yourself 'hearing' what you read as a voice in your mind), then dealt with in some way, which lets the brain use the input. Most often, visual scenarios are played out in the mind, simulating the real-life meaning of the text.

Cognitive levels can determine a great deal about how easy a topic or skill is to learn. If something is at a high cognitive level for a person, that person will experience more trouble learning it, and later using it. Cognitive levels in no way conform to any clearcut rules; they vary according to a persons experiences. But many similarities exist amongst people, because so many experiences are common to us all. For one, we learn spoken language long before written language. However, the two are connected to such an extent, that we place the written language 'on top' of the spoken, translating in our minds written words to spoken before truly dealing with them. Later in life, academic learning forces most to translate abstract concepts into something understandable before being able to work with it. The fact that most do not know they are doing this makes the translations clumsy and often rather random, making the topic studied seem much harder. Only luck decides whether you get a teacher or textbook capable of showing you how to reduce cognitive level of the topic.

Awareness of the cognitive level of any topic or skill is an advantage, because it will help you learn it more naturally and bind your new knowledge better to your existing knowledge. See how to reduce cognitive level for more info on this.