The sociological perspective is one that says that what people do and what they achieve does not happen in a vacuum. Instead, people's individual characteristics interact with larger social forces to create outcomes. This is one of the major points of Gladwell's book.
Gladwell illustrates this through a number of examples. One of these is his study of Canadian hockey stars. He points out that these stars tend to be born in the first three months of the year. This is because people born in those months got to be the oldest (and therefore biggest and strongest) in their age group in youth hockey. This led to them getting more coaching and more opportunities because they were believed to be more talented.
By looking at the importance of broader social forces and not just at individual actions, Gladwell is illustrating the use of the sociological perspective.