Hi! "He accompanied her" means that he came along with her. And "He was accompanied by her" means she came with him. They both mean that they were together. I'm sorry I can't explain it better. Cheers!

The question you need to ask is ' Who went along with whom? Obviously, you need more context to understand why someone want want or need another person to accompany them somewhere. For example, you could say: The Queen was accompanied by three ladies-in-waiting. or Three ladies-in-waiting accompanied the Queen. These would both have the same meaning, namely that the Queen went somewhere, and the three ladies-in-waiting went along with her to look after her. The reverse would not be likely. The most usual sentence in which we see this phrase is something like this: Children under 12 must be accompanied by an adult at all times. Or in other words, an adult must accompany the child. The child can enter the place in question, but an adult must stay with with them. or The criminal was accompanied by a police officer. A police officer accompanied the criminal. The person who 'is accompanied' is the one who has the reason or desire to go somewhere, while one who 'accompanies' simply goes along to help them, guide them, protect them or to keep them company. The two people have different reasons for going to the place in question.

He accompanied her means he wants to be with her. He is accompanied by her means she wants to be with her, but we don't know if he wants her to accompany her or not. More similar to this: He pursued her. Sure he likes her. He is pursued by her. Sure she likes him.

he accompanied her -- active voice he was accompanied by her -- passive voice