The right formatting of our code will make it easier to read and understand in case someone else needs to work with it. This is important, because in practice we will need to work in a teem with other people and it of great importance if we write our code in a way that our colleagues can quickly orient in it.
There are some defined rules for correct formatting of the code, which are collected in one place and are called conventions. The conventions are a group of rules, generally accepted by the programmers using a given language, which are massively used. These conventions help building norms in given languages - what is the best way to write and what are good practices. It is accepted that is a programmer follows them then his code is easy to read and understand.
The C# language is made by Microsoft and they are the people who define the best practices for writing. You should know that even if you don't follow the conventions given by Microsoft, your code will work (as long as it is properly written), but it will not be easy to understand. This, of course, is not fatal at base level, but the faster you get used to write quality code the better.