Ways to represent graph of nodes with text?

Some websites present a block of text for different tags or links that are popular, and each of these words have different font sizes, what is this called? It seems to me there aren't other compact ways to represent a graph in text mode. In 2D/3D graphs are represented with connected nodes, but when there are too many nodes the result is very cluttered. The most similar presentation in text mode is the directory tree, but it isn't compact, the list will grow vertically.