Good Friday is generally celebrated the Friday right before Easter. This is usually done in remembrance of what Jesus Christ did for us in sacrificing his life willingly on the cross. Therefore, many don’t understand why it is called “Good” Friday, since the event itself is so gruesome and horrible in many ways. The reason it’s called “Good” Friday is simply because this particular act of loving sacrifice, to Christians, is the pinnacle of Christ’s ministry. This is the moment that turned the course of human history from unbearable suffering in the afterlife to a chance to repent and return to heaven.
However, there is also some speculation that the holiday was originally named “God’s Friday”, and the word “good” in the name came from that, but the idea is the same.
