Building settlements & cities produce resources. Resources are produced when any player does a dice roll. Whomever has a settlement or a city in the border of the dice number will receive the resource shown in the tile. Settlements produce 1 resource, cities produce 2 resources.
When a player rolls a 7, they get to place the robber on any tile they wish and steal 1 random card from any of the colors adjacent to that tile. Robber prevents gaining resource from the tile it is on.