Simple past tense:
* I have seen that movie before. (You've seen the movie at some point in the past.)
* She has seen the Eiffel Tower. (She has witnessed the Eiffel Tower.)
* They have seen the Northern Lights. (They have experienced the Northern Lights.)
With a duration:
* I have seen that movie three times. (You have seen the movie multiple times.)
* We have seen the sunset over the ocean many times. (You've witnessed this event repeatedly.)
* He has seen his doctor every month for the past year. (He has had regular appointments.)
In a conditional statement:
* I have seen how this works, so I can help you. (Your experience gives you the ability to assist.)
* She has seen the error of her ways and is trying to change. (She has learned from her mistake and is improving.)
In a figurative sense:
* I have seen the best and the worst of humanity. (You've experienced both positive and negative aspects of life.)
* He has seen a lot of change in his lifetime. (He has witnessed major societal shifts.)
* She has seen things you wouldn't believe. (She has experienced extraordinary or unbelievable events.)
Remember, "have seen" is a present perfect tense verb, which means it describes an action that started in the past and has continued to the present or has an effect on the present.