Your Dashboard is your window to the behind-the-scenes side of your website. In the top left of your Toolbar you will see a Home Icon with the name of your Website next to it, if you click on this you will be redirected to the front-end of your live website where you can view any changes you have made in your dashboard.
If you are making a number of changes and wish to check after each one, it is a good idea to have two browser windows or two browser tabs open and to toggle between the two where one will show your Dashboard and the other your Live Website.
To clarify …
Your Dashboard lives here : http://www.yoursite.com/wp-admin/
Your Live Website lives here : http://www.yoursite.com/
Simply get both of those open in two browser tabs or windows to make and view changes easier.