Here you can set which leaderboard you want to look at you can select from the drop-down menu the following:
When more Matchmaker playlists have been created thier will be more options here
The search bar will allow you to search for specific players, but do take it in mind for the 1v1 & 2v2 Leaderboard it only shows players that have played within a month.
here is where it shows thier rank in the community, the player's name, How many games they have played and thier rating