Sanzen is a Japanese word that means "to meet with a teacher." It is a kind of teaching or practice that is used in Zen Buddhism. It is also sometimes called dokusan.
Imagine you have a really smart teacher who knows a lot about something you want to learn. You might ask this teacher for help and they might sit down with you and talk to you about what you're trying to learn. This is kind of like what sanzen is.
In Zen Buddhism, a person who is trying to learn about Buddhism might go to a Zen teacher and ask for sanzen. The teacher will usually sit in a special room and the student will come in and sit down in front of them. The teacher might ask the student questions or give them things to think about. They might also give the student special tasks or practices to do to help them learn more about Buddhism.
During sanzen, the teacher is like a guide who is helping the student on their path to understanding Buddhism. It's a bit like a big brother or sister helping out a younger sibling when they're learning something new. And just like with any learning, the more you practice, the more you'll understand and the better you'll become at it.