Samsung is discounting its popular 10,000mAh USB-C battery pack today, dropping the price down to just $15. That's good for around $19 off of its regular price. When it comes to battery packs under $15, you typically won't get this much capacity or USB-C connectivity. Both of which are great things to have, especially with most smartphones using USB-C now.
This battery pack from Samsung has a 10,000mAh capacity, which means it can charge your phone about twice, on a single charge before it needs some more juice. This is going to depend on how low the battery is when you charge it, and the capacity. But on average, it'll work for two full charges.
As far as ports go, there are two USB-A ports and then a USB-C port that can do input and output. But don't expect USB-C PD. For one, it would be a waste on a battery pack this small, and two, it wouldn't be in a battery pack that is this cheap. As that is newer technology and is going to cost a bit more.
You can pick up this Samsung battery pack from Samsung's website right now for just $15. It is only available in silver right now, and Samsung has not mentioned how long this deal will be available for, so you'll want to grab it before it is gone.