A reassurance marker is like a special message that tells you everything is going to be okay. Kind of like when your parents tell you that they will be there for you whenever you need them or when your teacher gives you a big smile and a pat on the back after you do a good job on your schoolwork.
Sometimes, when we feel worried or scared, it helps us to have something that reminds us that we are safe and loved. Reassurance markers are those things that can give us that feeling. They can be physical objects like a favorite teddy bear or a blanket, or they can be words that someone says to us like "I love you" or "Don't worry, everything will be alright."
So, whenever we feel afraid or uncertain, we can look to our reassurance markers and remember that we are not alone, and that we have people who care about us and want us to be happy and confident.