Instructional verbs are important to understand because they direct you in how to respond to a question. For example, you are just wasting words, time and energy if you explain an answer when the question only asks you to state a response. Understanding instructional verbs also makes sure you are responding to the whole question.
Be aware that definitions of instructional verbs can vary a little between subjects. Make sure you are familiar with the most common instructional verbs used in your subjects' exams and how you should respond to them.