Aspect is information described by a verb that is not related just to tense and time. For example, aspect shows whether an action is unfinished or not. It can be compared to tense, which refers to the verb's past or present form, and time, which is whether the verb refers to past, present or future.
Example
In English, aspects include the simple, the continuous and the perfect.
In the classroom
Teachers may take a functional approach to teaching each verb form, rather than looking explicitly at tense, time or aspect. For example, learners may study the uses of the present perfect continuous, or the past simple.
Further links:
https://www.teachingenglish.org.uk/blogs/dave-willis/tasking-present-perfect
https://www.teachingenglish.org.uk/article/catch-a-thief-past-simple-past-continuous-practice