Connectivism was introduced as a theory of learning based on the premise that knowledge exists in the world rather than in the head of an individual.
Connectivism proposes a perspective similar to the Activity theory of Vygotsky as it regards knowledge to exist within systems which are accessed through people participating in activities. It also bears some similarity with the Social Learning Theory of Bandura that proposes that people learn through contact.
The add-on "a learning theory for the digital age", that appears on Siemens paper  indicates the special importance that is given to the effect technology has on how people live, how they communicate, and how they learn.
See also the video from George Siemens explaining that the network is the learning: