The site is oriented toward affordable housing and community development applications. You can select a specific address, or a city, or even a census tract if you know its number, and then pick what you want to know about that location: area overviews, maps, data and charts, rankings or scatterplots. The default option is an Area Overview, a sample of which looks like this. (I picked Detroit, Michigan.)
The overview, which includes more than what is shown above, covers many demographic variables. Note the little charts to the right of each variable. You can mouse over the chart and get both a blowup of the chart and more information on the variable. Below is a population example.
Moving on to the mapping capability - on the right of the screen above, you have the ability to select data to map and what thematic colors to use. I chose to map total population, and selected rust for the color ramp.
My thematic map looks like this.
Now you can use the "Search for an indicator" capability to get more data. Clicking "Search" brings you a whole library of additional data. Each data source is a hyperlink to even more data.
One thing I like about this site is that it offers tasks you might want to do if you want information to help you evaluate an area, as shown below. It suggests stuff you might want to do like compare your location to other locations, make a map, make a scatterplot, etc.
So far everything I've described is available to any site visitor. However, you can access more capabilities if you're willing to complete a free registration. You can save places as favorites and save indicators to use again in further analysis. Registration also sets you up to do things like linking counties and aggregating their data. You can even create custom geographies from those available on the system.
Sometimes free stuff is worth what you pay for it. In this case, free gets you good looking maps, charts and graphs, and comparisons all in a good-looking format. These are maps, charts and data that you can easily use in a report or a presentation that will make you look good. It even has a help section that shows you how to use the site.