Moodle block that is used together with mod_astra. "Blocks are items which may be added to the left or right or centre column of any page in Moodle" (see Moodle docs and developer docs).
See the README in mod_astra for an overview of the plugin.
Directory astra_setup is copied to blocks directory in the Moodle installation. Moodle admin upgrades the database in the web user interface (site administration).