It's mainly verbs dealing with preference, perception and knowledge.
For example: like, prefer, see, hear, smell, taste, know, understand, feel, believe.
These are not generally used in the progressive tenses because they describe STATES as opposed to actions. For this reason they are sometimes called stative verbs.
The progressive tenses are used to describe actions ( e.g. I am playing, eating, dancing) rather than states. 'To know' is a state. You either know something or you don't - this isn't an activity, so you can't say 'I am knowing'.
But - and this is a big 'but' - there are many situations where some of these verbs do describe an activity. In these cases you can use them in the progressive tenses.
For example:
I love Brazilian music = This is a constant fact, so you can only use the simple form
I'm loving my new phone = This means I'm enjoying using it (at the moment), so you can use the progressive form
Sometimes it depends whether the verb is used in an intransitive or transitive sense:
This coffee tastes bitter = A fact, so you can only use the simple form
I'm tasting these cheeses to see which one I like best = An activity, so you can use the progressive form