"...The Thrift Savings Plan (TSP) for U.S. Government employees, and members of the military, will soon be opening a Roth TSP account access.
The difference under Roth is that your contributions are taxed at the front end, and your Roth TSP balance grows tax free, instead of the conventional TSP, in which your contributions are tax free, but you are taxed as ordinary income when you receive TSP distributions..."
Watch the following video to learn more.
Source: tsp.gov