psql is the standard command line interface for interacting with a PostgreSQL or TimescaleDB instance. Before installing psql, it's essential to confirm if you already have it installed. Installing psql on various platforms involves different steps depending on the operating system used, such as installing Homebrew on MacOS, using the apt package manager on Ubuntu and Debian, or downloading the installer from PostgreSQL.org for Windows 10. To connect to a PostgreSQL server, users need to provide connection parameters, including hostname, port, username, password, and database name, which can be specified in various ways depending on the desired approach. Once installed and connected, users can interact with their PostgreSQL instance using the psql command-line interface.