A: Having people over.
Q: So, you're having a party?
A: Kinda. I have a pool, a grill, and a random pile of alcohol. I'm not really organizing anything, just saying "come on over".
Q: So am I invited?
A: Sure. Come on over.
Q: Should I bring anything?
A: I'll provide burgers, hot dogs, and some soda. If you want anything else, or be sure I won't run out of the above, bring it. Suggested items include a bathing suit (or reasonable facsimile) and a towel.
Q: Are there fireworks?
A: I don't have any. But I do have a large backyard. This falls into the "if you want anything else category". Just don't bring anything that'll make my neighbors call the cops, please.