When a verb describes a state rather than an action, it’s called stative(state) verb, and it can only be used in simple tenses
I have a BMW.
(not I am having a BMW)
The verb "have" indicates a possession and it's used as a stative verb; so, we cannot use it in a progressive tense.
The roses smell nice.
(not the roses are smelling nice)
The soup tastes great.
(not the soup is tasting great)
Sometimes we can use the same verbs in a progressive tense, yet with a different meaning.
I am having a BMW soon.
Here the verb "have" doesn't indicate possession, it has a meaning of "buying".
I am tasting the soup.
Here the verb "taste" indicates an action so it is an action verb.See action verbs here
The flowers look beautiful. (state)
I am looking at the flowers. (action)
When I look at the flowers, I feel joyful. (action)
Some Common Stative Verbs
Also See:Stative Passive Verbs