Present perfect simple is used to talk about past events when the time is not specified.
He has appeared in several movies. He has acted in movies in the past but we don't know for sure when that happened. The time is not specified.
She has been to the theatre before. - we don't know when
He has worked there for a long time.
Past tense simple is used to talk about past events when the time has been specified.
He appeared in several movies last year. It is still a past action but you know when it happened, the time is specified here.
She went to the theatre yesterday.
He worked there last year. He worked there in 1987.