Board statistics are various pieces of information about your board such as the number of holes or the minimum trace width. You can view your design's statistics at any time. For example, you might want to view the number of holes in a board to try to reduce the hole count.

alt To view statistics for the currently active printed circuit board design:
  1. Choose Tools | Statistics.
    pcb-statistics-dialog.

alt "Components" is the overall number of footprints placed on the board. "Components Diversity" is the number of different footprint types.