The Locations widget shows you how many people are currently on your website right now and where they are visiting from.
The world map shows you where each individual visitor is located around the world.
The list of countries on the world map is ordered by the number of people currently online from that country right now. The list, as with everything else in GoSquared, is updated in real-time. So as soon as someone new from London visits your site, you'll see the number of people online from "United Kingdom" immediately increment by 1.
What do the coloured dots mean?
The colour of the dots represent how long somebody has been online for. It's a traffic light system where green means the visitor has just landed on your site, and red means they've been on the site for over 10 minutes. The longer they stay online, the colour of the dot fades from green, through yellow, to orange, and finally red.
How do I view which city they are from?
At the moment, city level data is only available in the People dashboard. In People CRM you can filter for users by city name and add a column to show you each uses' city in the list.