The 757 goals come from 3 different main categories:
Domestic tournaments, international tournaments and from the Brazilian national team.
In Domestic tournaments, Pele is said to have scored 656 goals from 702 matches, 24 international goals in 18 matches, and 77 goals for Brazil in 92 matches. This totals up to 757 goals.
Pele scored the goals in different ways as well. Santos (Pele's club) claims that he scored 643 official goals, and 77 goals for Brazil. The remaining 37 goals comes from the New York Cosmos, at the end of his career in USA. This totals up to the 757 goals as well. (Thank you Kerk).