Lexical aspect is like looking at verbs and seeing how they tell a story. Let's pretend we're playing with some toy cars. If I say "drive," that's a verb. But if I want to say how long or far each car will drive, that's the lexical aspect.
Imagine we have a yellow car and a green car. If I say "The yellow car drove to the store," that's a simple past tense. But if I say "The green car was driving to the store for hours," that's a different type of lexical aspect called continuous.
Basically, lexical aspect helps us understand how long or how much something happens when we use a verb. It's like using different colored markers to help us tell more about our story!