Spades is the partnership trick-taking game, and this is the free online version where you play against the computer. You sit opposite a computer partner, with two computer opponents to your left and right. Everybody bids the number of tricks they expect to win, spades are permanently trumps, and the side that makes its contract scores.
The opponents bid their hands properly, hold their trumps back, cover a partner's nil and stop taking tricks once the contract is safe, so the bidding genuinely matters. It is free, there is nothing to download and no sign-up, and an unfinished game waits for you in the same browser.
Yes. It is the traditional two-against-two game: you and a computer partner against two computer opponents. Your partner bids their own hand, covers your nil and keeps out of your way when you already hold the trick.
A promise to take no tricks at all in the hand. It scores 100 for your side if you get through untouched and costs 100 if you win even one trick. It is worth trying with short low spades, no aces and no bare kings.
Bags are tricks you win beyond your contract. Each one is worth a single point, which sounds harmless, but every ten bags your side collects takes 100 points straight back off the score. Bidding accurately beats overbidding and underbidding alike.
Not in the strict sense, since Spades is a four-player partnership game. Playing it here against the computer gives you what people usually mean when they look for solitaire spades free online: one player, nobody else to wait for, and a full game whenever you want one.