LTS (Long Term Support) release of Zabbix Agent proxy. Zabbix LTS releases
are supported for Zabbix customers during five (5) years i.e. 3 years of
Full Support (general, critical and security issues) and 2 additional years
of Limited Support (critical and security issues only). Zabbix LTS version release
will result in change of the first version number.

WWW: http://www.zabbix.com/life_cycle_and_release_policy.php