orbs and tablets

[Sokurah]

What are there weird orbs you randomly pick up?

Not the lvl up skill orb. I got one from a bell.

But rather some random orbs. Some seem to restore your HP. But io just picked up a purple one.

Also what do there tablets with a big face on them do? Charge up your mega move? (R2 i think) ? Does that mega attack also charge while attacking enemies? Its not really clear to me what these things do.

thx.