California allows friendly, social poker in a private home, but the rules that keep a home game legal are specific. Here's the plain-English version for hosts and players.
California Penal Code § 330 bans a specific list of banked and percentage games (faro, monte, roulette and the like). Player-vs-player poker is not on that list, which is why licensed cardrooms across the state can spread it.
No one, not the host and not a player, may act as "the house," banking bets against everyone else or taking a percentage. The game must be strictly player-against-player.
Penal Code § 337j targets running a gambling operation for profit without a license. A social game where the host earns nothing from the play itself stays on the right side of that line.
A legal game is still bound by the law against fraud. Penal Code § 332 makes it a crime to win someone's money by cheating: marked cards, sleight of hand, collusion, or any trick outside the rules. Depending on the amount taken, it can be charged as a misdemeanor or a felony.
California has a deep-rooted policy against enforcing gambling debts, and it applies even to a legal game. Under Civil Code § 1667 a wager made on credit is not something a court will help you collect. That's the real reason a home game runs on table stakes: buy in with cash, play the chips in front of you, and settle up on the spot.
Players should be 18+ (21+ where alcohol is served, as it is here). Some cities and HOAs add their own restrictions, so a genuinely private, invite-only game is the safe default.