PgAgent is a basic scheduling agent that comes packaged with PgAdmin III (since pre-8.0 or so) and that can be managed by PgAdmin III.
PgAdmin III is the database administration tool that comes packaged with PostgreSQL.
For those familiar with
unix/linux cronjobs and crontab structure, PgAgent's scheduling structure should look very familiar.
For those familiar with using Microsoft SQL Server Scheduling Agent or Windows Scheduling Tasks, but not used to crontab structure,
the PgAdmin III Job Agent interface to PgAgent should look very welcoming, but the schedule tab may look a little unfamiliar.
PgAgent can run both PostgreSQL stored functions and sql statements as well as OS shell commands and batch tasks.