Types of blocks in the `pg_stat_statements`

Greetings.

I cannot get understanding about what different types of blocks means here:
http://www.postgresql.org/docs/current/interactive/pgstatstatements.html

I assume, that `shared` are blocks from the `shared_buffers`
and `temp` are blocks used by temporary files (absence of `dirtied` and
`hit` also speaks for this).

But what `local` blocks mean?

--
Victor Y. Yegorov