What do you mean by league match or round robin tournament?

League: These are also called Round Robin Tournament. In league system all the teams are treated at par in league tournament. There are two types of league tournaments:
Single league tournament
Double league tournament

Single league tournament: In this type of tournament, every team shall play once with every other teams. The total number of matches in a single league tournament shall be [(n) (n – 1)]/2.

For example, if 8 teams are competing, the total number of matches to be [(8) (8 – 1)]/2 = 4(7) = 28.

Double league tournament: In this type of tournament, every team shall play twice with every other team. The total number of matches shall be n(n – 1).

For example, if 8 teams are competing the total number of matches to be n(n – 1) = 8(8 – 1) = 8(7) = 56 matches.

League: These are also called Round Robin Tournament. In league system all the teams are treated at par in league tournament. 

There are two types of league tournaments: 

(a) Single league tournament 

(b) Double league tournament

(a) Single league tournament: In this type of tournament, every team shall play once with every other teams. The total number of matches in a single league tournament shall be n(n-1)/2.

For example, if 10 teams are competing, the total number of matches to be played shall be n(n-1)/2 = 10(10-1)/2 = 10(9)/2 = 45 matches

(b) Double league tournament: In this type of tournament, every team shall play twice with every other team. The total number of matches shall be n (n - 1), r.g., 10 teams are competing the total number of matches: n (n - 1) = 10 (10 - 1) = 10 (9) = 90 matches.