Is 30W enough to fast-charge my phone?

For most USB-C phones, yes. Many phones charge at 18W to 27W, so a 30W charger covers them. iPhones top out lower, so you will not see the full 30W.

Can it charge a laptop?

Only small, low-power laptops. Most USB-C laptops want 45W to 65W or more, and a 30W charger will charge them slowly or not at all under load.

Does it come with a cable?

Belkin sells this as a wall charger only in most packs. Check the box contents before buying, since you will likely need your own USB-C cable.

What is Quick Charge 3.0 good for?

It speeds up charging on older Qualcomm-based Android phones. Newer phones use USB Power Delivery or PPS, which this charger also supports at up to 30W.

Is $19.99 a good price?

It is a typical price for a branded 30W single-port charger. Generic 30W chargers often cost less, so pay the premium only if you want the Belkin name.