Aupasana is a very old tradition from India where people go to a quiet place, sit down and focus all their attention on something that they consider sacred or divine. This can be a god or goddess, a holy book, or even just the feeling they get when they think about spirituality.
It's sort of like when you're playing a game and you're really into it, and all your attention is on the game. Except in Aupasana, instead of a game, you're thinking about things that are really important to you, and you're trying to connect with those things in a deeper way.
People who practice Aupasana believe that it can help them feel more peaceful, more connected to their spirituality, and more understanding of themselves and the world around them. It's not always an easy thing to do, because it requires a lot of focus and quiet time, but for those who love it, Aupasana can be a really beautiful and meaningful practice.