When you say you know a word or phrase, you could mean one of two things. First, you could mean that if someone says the word to you, you know what it means. This is passive knowledge. The second way of knowing is that you can recall and use that vocabulary appropriately. This is active knowledge.
This isn’t anything to do with active or passive voice in grammar. It’s about how you store your memory of a word for later use, and there’s a large, important difference.