Like leerspace said, the IPFS protocol doesn't use blockchain directly. However you may hear IPFS and blockchains talked about together quite frequently. Many blockchain projects use IPFS to increase their storage capacity, while still maintaining the tamper-proof audibility that comes with blockchains.
I wrote a blog post on this that might explain this a bit: Ethereum and IFPS
As I mention in the post, it's a bit high level of an explanation, so if you have any deeper technical questions, I'd be more than happy to help answer them.