Skeuomorphism intends to solve a problem common to designers and developers: How do you design software experiences that users can learn quickly and use easily? The skeuoporphism answer is to make the software seem inherently easy to use by making graphic elements look like things users are already familiar with.
For example: If youre making an online notebook, you might design it to look like a stack of papers bound together by a spiral ring. Youre assuming that users will understand that the pages are part of a system and it is possible flip them.
Some designers really hate this approach and some love it. It made a lot of sense to make an online calendar look like a desk calendar when it was a new technology, but not so much anymore.