A slogan in heraldry is like a special message or saying that is added to a coat of arms. It's like a secret code that helps to describe the important qualities or values of a family or group.
Imagine you have a special toy that is really important to you. Your mom says it's yours and only yours and that nobody else can take it from you. That's kind of like a slogan on a coat of arms, it's something that tells other people, "Hey, this family is important and we stand for something special."
The slogan usually goes at the bottom of the coat of arms, kind of like when you write your name at the bottom of a picture you drew. It can be in any language, and it's often written in fancy letters.
So, if your family had a coat of arms, you might have a slogan that says something like "Brave and True" or "Always Strong". It's like a little message that tells people what your family is all about.