Vacuum

Vacuum reclaims storage occupied by deleted tuples. In normal PostgreSQL operation, tuples that are deleted or obsoleted by an update are not physically removed from their table; they remain present until a Vacuum is done. Therefore it's necessary to do Vacuum periodically, especially on frequently-updated tables.

Vacuum Database
Just simply right-click the database and select Maintain Database -> Vacuum Database... -> desired option.

Vacuum Table
Just simply right-click the table and select Maintain Tables -> Vacuum Tables... -> desired option.

Parameters
Full Selects "full" vacuum, which may reclaim more space, but takes much longer and exclusively locks the table.
Freeze Selects aggressive "freezing" of tuples.
Analyze Updates statistics used by the planner to determine the most efficient way to execute a query.
Verbose Prints a detailed vacuum activity report for each table. (Default enabled in Navicat)

Outputs
When Verbose is specified, Vacuum emits progress messages to indicate which table is currently being processed. Various statistics about the tables are printed as well.

Related topics:
Analyze
Reindex