This coursera course was taken down, but it is now up and running at lagunita.stanford.edu [0], which uses edx's open source platform [1]. The same happened to other stanford courses previously on coursera, you can find them here [2], including Compilers, Automata Theory, and Convex Optimization.
Yes, in general what they refer to are things like the IRS Tax records (250 TB), Yahoo Ad data (900 TB). You just can't use a single machine to work with such data.
[0] https://lagunita.stanford.edu/courses/course-v1:ComputerScie...
[1] https://open.edx.org/ https://github.com/edx/edx-platform
[2] https://lagunita.stanford.edu/courses