We can think of holiness as living in a way that is pleasing to God. As the Bible says, "Be perfect, therefore, as your heavenly Father is perfect" (Matthew 5:48). This doesn't mean that we are sinless, but it does mean that we are striving to act in ways that reflect the character of God. One way to help children understand this concept is to compare it to being like Jesus. Just as Jesus was sinless and perfect, we too are called to live holy lives. This doesn't mean that we will be perfect all the time - just as Jesus wasn't - but it does mean that we should always be striving towards holiness.