1. A method comprising: accessing, using one or more processors associated with one or more computing devices, a social graph comprising a plurality of nodes and a plurality of edges connecting the nodes, wherein each edge between two nodes represents a single degree of separation between the two nodes, the plurality of nodes comprising: a first user node corresponding to a first user associated with an online social network; one or more second user nodes corresponding to one or more second users associated with the online social network, respectively, wherein each of the second user nodes is within a threshold degree of separation from the first user node; and one or more concept nodes corresponding to one or more concepts, respectively; identifying, using the one or more processors, a first set of concept nodes that are connected to one or more of the second user nodes by one or more edges, respectively, wherein each of the concept nodes in the first set of concept nodes is associated with an application accessible by users associated with the online social network; selecting, using the one or more processors, a second set of concept nodes from the first set of concept nodes based on edges connected to the concept nodes; and generating, using the one or more processors, an advertisement for the application, the advertisement comprising information representing one or more concepts corresponding to one or more concept nodes, respectively, in the second set of concept nodes.