When will the block exchange by BitSwap?
In the IPFS white paper, it was written that blocks were exchanged by BitSwap.
In my understanding is, The block is
・Uploaded data itself
・Files linked to Merkle dag format
・ Or part of the file divided into Merkle dag format
It seems to be written that these blocks are distributed among nodes.
When will it be distributed (or exchanged?)?
If it is distributed when another node downloads the file,
After downloading the file
・Nodes distributed by BitSwap
the file (or part of it) is cached and distributed in above nodes?
is this understanding is correct?