Ionide generates VSCode Launch Configurations for running and debugging each runnable project in your workspace. Generally this means projects with a ProjectType of Exe. These autogenerated configurations act essentially the same as running dotnet run in the project's directory.
Ionide will generate additional launch configurations for any projects that have a Properties/launchSettings.json file. This file is often generated by Visual Studio, but can be generated manually as well. These launch settings profiles can be run by Visual Studio, dotnet run, dotnet watch, and JetBrains Rider, and now VSCode joins the bunch! Any launch settings profiles with a commandName of Project can be run, and any applicationUrl, environmentVariables, and commandLineArgs settings will be used.
The generated launch configurations will set a preLaunchTask dependency on the Build task for their associated project, so you'll always run the most up-to-date build before running your code.
To explicitly run one of the new launch configurations, choose the Debug menu, and select a configuration from the drop-down menu. From there, you're all set!