*(From JP 1-02, Department of Defense Dictionary of Military and Associated Terms, www.dtic.mil/doctrine/new_pubs/jp1_02.pdf.) Operations security (OPSEC) is a process of identifying critical information and subsequently analyzing friendly actions attendant to military operations and other activities to: (a) identify those operations that can be observed by adversary intelligence systems; (b) determine what indicators adversary intelligence systems might obtain that could be interpreted or pieced together to derive critical information in time to be useful to adversaries; and (c) select and execute measures that eliminate or reduce to an acceptable level the vulnerabilities of friendly actions to adversary exploitation.

In normal human terms:

Operations security, also known as OPSEC, is where I think about what I'm about to say before I say in order not to give out too much information to the bad guys.  Specifically information, even in its smallest, most innocent forms, that can be pieced with other information to give a complete picture for the enemy that can be used against me, Mr. Smartypants or the rest of the US Armed Forces. 
During WWII OPSEC was achieved with the slogan, "Loose Lips Sink Ships".  I heard somewhere recently that it had been updated to, "Loose Tweets Sink Fleets"  This is why you will not see me use my husband's first name, nor will you ever get a good look at his uniform or his rank.  I won't talk about where he is, or exactly when he left or is due back.  As a blogger, I walk a fine line between giving you enough information to keep you interested and involved in our lives and too much information that could endanger my husband or the soldiers he serves with. 
With all of that said, I beg of you to actively participate in OPSEC with me.  If you know us personally, please don't comment about my husband's status.  If you ask questions, please don't be offended if I don't answer.  I take my jobs seriously.  I love blogging and want to keep doing it, but I have priorities.  I am a wife first, American second and a blogger third.  There is no room for exceptions to this policy.  Thanks for understanding.