I want to be able to show website progress to clients but don't want to have server running all the time... Is shutting off the website option the only way to stop it or can I shut down the whole server?
You can shut off websites in Server.app using the "Websites" controller", but I don't know why you would want to. Its made to run all the time, and hardly uses any processor power. If you want to see how much power the web server is using, open Activity Monitor in Utilities, select "All processes" upper right and type "httpd" in the filter field. It will almost always say it is using zero processor, because it idles while listening for a request.
I understand that it uses very little resources but is that the only way to stop the site?... Can't the whole server be shut down as a whole or is the only way to shut off each service individually? I do freelance web design and only want the server to show clients progress on projects occasionally so I wanna be able to turn it on to let them check it out and shut it down afterwards... I have no need for it to be running constantly no matter how little resources it uses.
It's not clear what you mean by "site". Services can be disabled in the Server.app interface, including the Apache webserver:
Notice that every service has an On/Off feature. You can shut off Apache if you only need it occasionally. Server.app still leaves a listener daemon running in the background which is not advisable to disable unless you are uninstalling the application.