There are three groups of English verbs:
1. Normal verbs which describe physical actions like "run" and "walk" and can be used in all tenses.
2. Non-continuous verbs which describe non-physical concepts like "want" and "need" and are rarely used in continuous tenses.
3. Mixed verbs which have multiple meanings, some behaving as non-continuous verbs and others as normal verbs, such as "appear", "feel", and "see". Mixed verbs can be confusing because their meaning and usage depends on context.