This map is a depiction of the results of the 2016 presidential election. Intuitively, we know that blue represents democratic votes and red represents republican votes. In this case, white represents areas that have more balance between democratic and republican voters.
For this map, we normalized the data available by placing more weight on counties with higher population densities. These areas can be seen in bright colors. On the other hand, counties that have comparatively very few people where area of land are shown in darker colors because these areas are simply not as representative.
Throwing it back to 2012 to ass some perspective, one can see many of states throughout the country that were the deciding states for the 2016 election. For many states during the presidential elections, we know which way they will vote before it happens because they are consistent in their politcal values-- New York is a good example of a state that always votes democratic. For this reason, the elections are generally decided by the less decisive states, many of which can be seen in the Midwest. Barack Obama won over the majority of hearts in the 2012 elections, but we can see in 2016's controversial presidential race how those more moderate states can sway the elections either which way.