Capsules are a type of verse found in The Final Existence and they contain a lot of light (more specifically Absolute Lights). Their barriers are extremely hard (around LY thick) and the only known place where they are found broken is in places with a high Capsule density, causing lots of collisions. They are also one of the only known barriers that can contain The Absolute Light due to the forces caused from all the photons.
The name 'Capsule' was originally named because they were found in The Final Existence and people were wondering what was inside, so the name 'Capsule' was chosen because it was assumed it contained something. It turns out it was a verse that was already discovered, but the name's origin is interesting nonetheless.
It is currently unknown what a Capsule's barrier is made out of. The composition is likely similar to that of a Lockverse, although a weaker version of it.