"Lit” is a slang term used by Millennials to describe "a certain situation, person, place, or thing as awesome/crazy or just ‘happening’ in general.”  For example, "TACO BELL was so lit last night, I had to wait in line for 15 minutes before I could order.”

"Throwing shade” is a slang phrase used to publicly denounce or disrespect a person.

"On fleek” means "on point.”

Want more "millennial speak?”  Google Urban Dictionary.