The Humble Monthly bundle is on the way out, and will soon be replaced by a new service called Humble Choice, which will be more expensive to everyone except existing subscribers.
Currently, the monthly bundle costs $12 for a handful of mystery games, including a couple of early unlocks that are usually better-known titles. Under Humble Choice, you'll be able to choose the games you keep from a wide selection: you'll keep three games if you sign up to the $15/month basic plan, or nine games if you pay $20 a month for the premium subscription. The company hasn't said how big the selection of games you'll pick from will be.
If you're already signed up to the Humble Monthly bundle before the services switch over, which will happen "later this year", then you don't need to worry: you'll keep paying $12 monthly on a "classic" subscription plan, and you'll keep 10 games per month. Any discounts you currently earn by paying for multiple months at a time will carry over. But if you cancel your classic membership after the switch to Humble Choice then you won't be able to get it back, and you'll have to resubscribe as if you were a new customer, the company said in an FAQ.
The premium and classic plans get 20% off at the Humble store plus unlimited access to Humble-published "Humble Originals" and betas. The $15 basic plan gets 10% off at the store plus unlimited access to games Humble publishes, including betas.
The cheapest tier is the Lite subscription, but you don't get to keep any games monthly: you're just paying $5 for a 10% store discount, access to Humble-published games and the Humble Trove, a rotating selection of 60+ games that you can browse here. The Humble Trove is included in all other packages, too.
You can see what each tier gets in the grid below (click the full-screen button to read the detail). You'll be able to "pause" your subscription at any time, just like with the Humble Monthly bundle.