When did you become someone that needs spoon feeding?
To recap, there are four types of data related to the blockchain in the bitcoin system: the raw blocks as received over the network (blk???.dat), the undo data (rev???.dat), the block index and the UTXO set (both LevelDB databases). The databases are built from the raw data.
Block pruning allows Bitcoin Core to delete the raw block and undo data once it's been validated and used to build the databases.
https://github.com/bitcoin/bitcoin/blob/v0.11.0/doc/release-notes.md#block-file-pruningi know i know as i said before, that the real definition of pruning was as you said..
but the 550mb has got alot of people into a pickle that it must cut out some of the UTXO (laymens:unspent) to get to a possible level of 550mb hard drive space.
it needs to be clarified better that the 550mb is not total hard drive storage allocation of everything related to the blockchain but the separate parts related just to recent data that can change. and not related to archival data of unspents.
it may be wrote down in some places as far back as 2013-4-5 when the term pruning first came about. but the 2016 info on the actual release has made some left in a pickle thinking v0.12 is not the same as the original definition of pruning