I'm not sure what "Hazing" is (possibly the move Haze?)
But yes, EVs are effort values,
• OU is a tier in competitive play for basically Standard Pokemon to use.
• Sweeping is when a Sweeper (a Pokemon usually with high attack and speed mainly used for attacking) does its job and just starts to KO a bunch of Pokemon.
• OHKO stands for "One Hit KO" which are moves or attacks that will KO a Pokemon in one hit, usually referring to Sheer Cold, Fissure, Guillotine, etc.