The 'About Koha' area will give you important server information as well as general information about Koha.
Get there: More > About Koha
Under the 'Server Information' tab you will find information about the Koha version and the machine you have installed Koha on. This information is very important for debugging problems. When reporting issues to your support provider or to the various other support avenues (mailing lists, chat room, etc), it's always good to give the information from this screen.