When you are using scripting in Unity, you are communicating with the Game Engine and asking it to perform actions. To communicate with the system, you are using a language or a set of words bound by a syntax that the computer and you know. This language consists of keywords, key phrases, and a syntax that ensures that the instructions are written and (more importantly) understood properly.
In computer science, this language needs to be exact, precise, unambiguous, and with a correct syntax. In other words, it needs to be exact.
When writing C# code, you will be following a syntax; this syntax will consist in a set of rules that will make it possible for you to communicate with Unity clearly and unambiguously.In addition to its syntax, C# also uses classes, and your C# scripts will, by default, be saved as classes.