Lying in state means that the body of an important person who has died is placed in a special place where people can come and pay their respects. It's like when you have a special toy that you love and you want to show it to your friends, except in this case, it's a person who was really important to a lot of people.
When someone important, like a president or other leader, dies, they usually get to lie in state at a special building, like a government building, a museum, or a church. The body is placed in a special box called a casket, which is decorated with beautiful flowers and flags.
Lots of people come to see the body and show their respect, and they might say a prayer, leave flowers or a card, or just stand quietly for a little while. It's like when you go to a funeral or visitation, but instead of happening at a funeral home, it happens in a special public place.
Lying in state is a way for people to remember and honor someone who was important, and to show that their contributions to their community or country will not be forgotten.