Where can I find the explanation of each field of the result returned by the api of blockchain.info?
You can find the documentation for that call, such as it is, here. It's not very helpful.

I can give you a few tips, though.


n is the vout of the input. A vout plus a txid unambiguously specify a transaction output, and are collectively known as an outpoint. More.
tx_index is a field used by blockchain.info, and has no meaning outside of blockchain.info's api.
No idea what type means. Looking at a few transactions at random, it always seems to be zero.