Paul Baran was a Polish-American computer scientists who is credited as co-developing the idea of (independently) packet switching for computer networks and communication systems. Packet switching is a technology for transferring data across digital systems; using small "packets" of data. Packet switching was first implemented into two revolutionary computer systems.
Both of these computer networks were designed and built in the late 1960's (1968-1970). Paul Baran was influential in inspiring American computer scientists into implementing packet switching into ARPANET; while Donald Davies (independent co-inventor of packet switching) inspired UK computer scientists to create the Mark I network. ARPANET evolved to become the modern Internet; therefore Paul Baran is viewed as being one of the pioneers of the Internet.
Paul Baran was born into a Jewish family in what constituted Poland (the city he was born into is now part of the Republic of Belarus) in 1926. Baran's family emigrated to the United States of America when he was two year's old. Baran studied engineering, and worked within engineering communication systems. While working at the RAND corporation in the 1960's, Baran was tasked with developing a communications system which could survive a nuclear attack. Baran did this by proposing a system which sent data in separate "packets"; Baran termed these "blocks". These "packets" are routed (in a packet switching system) through nodes; each node decides where the packet should be sent, and can route a packet "around" a node (if it's been damaged in a cold war nuclear attack for example, as was Baran's objective).