What does the '@' symbol represent in a MySQL user account specification (e.g., 'user'@'host')?

The '@' symbol separates the username from the host from which the user is allowed to connect. 'user' is the username, and 'host' specifies the allowed host(s). '%' acts as a wildcard, meaning the user can connect from any host. Specifying a specific IP address or hostname restricts the user to connecting only from that location.