Pietism is a way of being a Christian that focuses on having a personal relationship with God. It first started in Germany in the 17th century and became very popular in the 18th century.
Think of it like having a best friend or a really close family member. You spend time with them, talk to them, and really get to know them. Pietism is like that, but with God.
People who follow pietism often spend a lot of time praying and reading the Bible. They believe that these things help them to connect with God and understand what He wants for their lives.
Pietists also believe that it's important to live a "holy" life, which means trying to live in a way that is good and pleasing to God. This might mean doing things like treating others kindly, helping those in need, and avoiding behaviors that are harmful or sinful.
One example of a famous pietist is a man named Philipp Spener. He believed that the church should focus more on personal faith than on strict rules and rituals. This idea became very popular, and many people started to follow his teachings.
Overall, pietism is all about having a personal, meaningful relationship with God and living in a way that honors Him.