When you create a script and attach it to a GameObject, the script appears in the GameObject’s Inspector just like a Component. This is because scripts become Components when they are saved - a script is just a specific type of Component. In technical terms, a script compiles as a type of Component, and is treated like any other Component by the Unity engine. So basically, a script is a Component that you are creating yourself. You will define its members to be exposed in the Inspector, and it will execute whatever functionality you’ve written.
Узнайте больше о создании и использовании скриптов на странице Скриптинг.