Resharpher is a popular in a visual studio because it will find compiler errors, runtime errors, redundancies, and code smellsas you type, suggesting intelligent corrections for them.
ReSharper helps you explore code by visualizing the structure of files, type and style hierarchies, call and value chains, project dependencies. It allows you to instantly traverse your entire solution and jump right to the exact file and line that you are looking for, decompiling library code if necessary.
Dozens of solution-wide refactorings are available to help you safely change your code base. Code formatting and cleanup features allow you to get rid of unused code and help your entire team to ensure compliance to coding standards.
In short it is also called intelligence of compile which help you in coding it is make coding easy by giving suggetion.