Imagine you did something bad and you feel really guilty about it. You want to say sorry to God and make things right again. In the old days, people had a special way of doing this, called a "sin offering."
Here's how it worked: first, you would pick an animal, like a sheep or a goat. You would bring this animal to a special place called the altar. Then, you would put your hands on the animal's head and say a prayer, asking God to forgive your sins.
Next, you would take a knife and kill the animal. This might seem scary or mean, but it was an important part of the sin offering. The idea was that the animal was taking the punishment for your sins, like a substitute.
After the animal was dead, the priest would take some of its blood and sprinkle it on the altar. Then, the priest would burn the rest of the animal on the altar, sending smoke up to heaven. This smoke was like a message to God, telling Him that you were sorry and asking Him to forgive you.
So, a sin offering was a way for people to make things right with God when they had done something wrong. By sacrificing an animal, they were admitting their guilt and asking for forgiveness.