What does separation of church and state mean?

The separation of church and state is the principle that the government must maintain an attitude of neutrality toward religion.  

Many view separation of church and state as required by the First Amendment because it not only allows citizens the freedom to practice any religion of their choice but also prevents the government from officially recognizing or favoring any one religion.  

Explanation:

The government cannot make laws based on religion.

Explanation:

Not allowed to draw on walls
You can say/

This rule allows the house to stay in order and clean. It also ensures a clean environment to live in. If we could draw on walls then the house would be full of scribbles and it wouldn’t look nice.

Things like that basically.
Hope I helped