[has/have + past participle]
We use the Present Perfect to say that an action happened at an unspecified time before now.
You can use the Present Perfect to describe your experience. It is like saying, "I have the experience of..." You can also use this tense to say that you have never had a certain experience. The Present Perfect is NOT used to describe a specific event.
We often use the Present Perfect to talk about change that has happened over a period of time.
We often use the Present Perfect to list the accomplishments of individuals and humanity. You cannot mention a specific time.
We often use the Present Perfect to say that an action which we expected has not happened. Using the Present Perfect suggests that we are still waiting for the action to happen.
We also use the Present Perfect to talk about several different actions which have occurred in the past at different times. Present Perfect suggests the process is not complete and more actions are possible.