Apprehension and comprehension may be similar words, but they have two completely different meanings. Apprehension is referring to when someone may feel nervous about something. An example of using the word is "John had to go to driving school tomorrow, but he had some apprehension as he has never driven a car before." Here you can see John is nervous about his first day of driving. Comprehension is a word that means to understand something. An example of using the word is "Cynthia had great reading comprehension skills for a first grader." This means she is at a high level of understanding of the subject of reading.
Typically, when using the word apprehension, you are referring to being in a state of trepidation about whether to do something or not. For example, someone could be apprehensive about flying in an airplane for the first time, and they may feel apprehensive about it.
However, it could also refer to a mental state in which we are conscious of something yet fail to fully understand the concept of what is being said or done and not passing any judgment. Comprehension also means understanding something, particularly in the fields of education or psychology.
It involves a psychological process in which a person is aware of an abstract or physical item, such as a message. It also includes how a person might perceive a situation, and if he or she recognizes a command or instruction.