If something is creased, it has lines in it from being folded or crushed.
Creased things are usually not very neat or tidy.
Examples:
The paper is creased from being in my pocket.
She creased her skirt by sitting on it.
The creased map was hard to read.
I look creased after sleeping on the couch.
The creased shirt looked like it had been in a fight.
The creased paper made the teacher mad.