Environmental security is the tracking of changes in your system, and the evaluation of the effectiveness of the security controls you have enacted, to provide an overall awareness of the attack surface of your environment.
The attack surface is the amount of exposure your system has that could contain a vulnerability, which could be exploited by an attacker. Exploits are categorized as attack vectors that are used to target those vulnerabilities.
Data security (including encrypted connections and encrypted files) and user access (including restricting access and implementing security controls like password policies) can help to reduce your attack surface. Monitoring the configuration of your system and routine system maintenance, including a review of access logs and user histories, can also reduce your attack surface and increase an overall awareness of your environment.