It's a bit clunky in the editor here at Codecademy, sometimes the default code uses spaces and sometime it uses tabs. I tend to go with tabs here.
The point of spacing is for humans, not the browser, so when you are coding on your own machine or webserver, you will be using a code editor that you can configure to suit yourself or your team's/company's standards. You will be able to set it to auto tab, and you will be able to set it to 2 or 3 or more spaces per tab.
The name of the div doesn't matter to the browser but you should be kind to the other humans reading your code, including yourself. Don't name your divs "Fred" and "Barney". Don't name them "green-background" because when you decide to change that background to orange someday that is going to be really silly looking. Same for something like "left-column". It might sound like a good idea in some cases, but then you decide to move the content to the right, or the bottom. Names that describe the purpose will be more sensible, "nav-bar", "contact_info", "social_media". There is a ton of reading about this on the net.