The following websites offer tactical puzzles and/or the facilities to play chess on-line. Some features are accesssible free of charge.
Sites useful for learning to play or improving your chess. Some are entirely free, others are free at beginner levels.
(The Official Laws of Chess)
FIDE Laws with comments for Arbiters - CAA
FIDE Arbiters' Manual 2018
Here are some books worth considering. To buy them, please see the online shopping links on the Links page:
For learning opening strategy: