This document discusses key concepts in social network theory including networks, ties, weak ties, strong ties, structural holes, and role sets. It summarizes:
1) Social networks are made up of nodes (actors) connected by ties. Unlike groups, networks have no boundaries and can be disconnected parts that become connected over time.
2) Weak ties, or acquaintances between different social circles, are important for bringing new information and opportunities. Strong ties within one's own social circle provide trust and cohesion but less novelty.
3) People who bridge "structural holes" between different networks, usually via weak ties, gain access to diverse information and ideas that help them succeed and innovate.