It's for (2): binding the MSBuild solution to the server synchronises the ruleset used in Visual Studio with the Quality Profile defined in SonarQube. The goal is to have the same set of issues appearing in the IDE as would appear when an analysis is run on a CI machine and pushed to SonarQube. Note however that the issues will be slightly different due to some current limitations e.g. parameterised rules are not run in the Visual Studio at present as the connected mode doesn't yet synchronise the necessary configuration).
In addition, when a Visual Studio solution is bound to a SonarQube project, issues that are suppressed in SonarQube will not be reported in the IDE, and notifications will be displayed in the IDE when the quality gate changes.
