|The following information is from the Adventure Time comic book series.|
It may not be part of the same canon or continuity as the animated series.
The Bag of Holding is a magical object that can hold everything inside of it. It pulls in everything around it. The Snail freed The Lich from the bag, and began to use it to destroy everything on the planet. The bag can pull in very deep parts of the ground. The path it leaves is a deep and narrow canyon, as it even pulled out ancient layers of Earth with dinosaur fossils and mammal skulls. The bag appears to stop absorbing things when no one is using it. Finn, Jake, Ice King, and the entire Candy Kingdom end up getting sucked into the bag. Finn and Jake meet Desert Princess inside it. The bag transports things and people into random locations in it, but Finn and Jake stayed together because they were in "Jake Suit mode."
The bag was destroyed by Jake when he used a hole they'd made at the bottom of the sack to loop round and tear it open, releasing everything it took in.
The bag of holding appears to be a violet pouch with a yellow rope to hold and to close the bag together.
The inside of the bag is wide and high, however the bottom of the sack can be reached.