How does merging work?

See merge

What are some best practices for distributed development with Mercurial?

See WorkingPractices

How do I import from a repository created in a different SCM?

See ConvertingRepositories for various tips.

What about Windows support?

See WindowsInstall for getting started using Windows.

Is there a GUI front-end?

See OtherTools for information on graphical merge tools and other front-ends.