MSDeployThis activity uses msdeploy to deploy packages generated by visual studio/tfs "Build Deployment Package" command. You can specify whether to use the generated .cmd file (see notes below) or msdeploy.exe directly.
Pretty self explanatory if you look at the screenshot and tooltips.
Note about MSDeploy activity and VS2010 SP1
The activity uses the cmd file generated by visual studio "Build Deployment Package" command. There's currently a bug in this process, to fix, see :
http://support.microsoft.com/kb/2537134
Note about MSDeploy activity and VS2012
Another bug in the .cmd file that looks like the same one as above.