Blockchain data storage
How does IPFS use Blockchain
https://ipfs.io/#how says

Blockchains
IPFS and the Blockchain are a perfect match! You can address large amounts of data with IPFS, and place the immutable, permanent IPFS links into a blockchain transaction. This timestamps and secures your content, without having to put the data on the chain itself.

So yes, IPFS is separate from the Bitcoin blockchain but it seems you have the option of embedding a hash in a Bitcoin transaction (for which the usual fees are needed) as proof that the hashed data existed at a point in time.
The Bitcoin blockchain is a journal of Bitcoin currency transactions. Small items like hashes can be included in the transaction details that are recorded but you pay a fee per byte and you need to have a funded wallet.

Related Questions

What methods are currently used to embed additional data into the Bitcoin blockchain?