The shell bone script of character Display is
The T is a simple table, the 一 on the top indicates the sky or the god in the sky. People may put something (goat or ox) on the table to worship god for advice or protection. The original meaning is to pray to god or sky for advice and protection.
The above is my explanation. The meaning of the character is disputable, there are some different explanations, but there is one thing in common: it is a communication between human being and the god.
The bronze script of the character is
only the table, no sky.
The big seal script of the character is
Actually, 示 means Show too. It is often used with another character of Show - 显 to form a combination word: 显示, which means Show. 显 is more like a Show off of a person, 示 is more like a Show of something by people. But most of time, they are exchangeable.