Even having family that has served, what exactly does a CSM Do?

James Adair this is a link on the rank:
https://en.wikipedia.org/wiki/Sergeant_major

COMMAND SERGEANT MAJOR AND SERGEANT MAJOR: Enlisted soldiers who attain the distinction of being selected to be command sergeant major are the epitome of success in their chosen field, in this professional of arms. Except sergeant major of the Army, there is no higher grade of rank for enlisted soldiers, and there is no greater honor.

The command sergeant major carries out policies and standard of the performance, training, appearance and conduct of enlisted personnel. The command sergeant major advises and initiates recommendations to the commander and staff in matters pertaining to the local NCO support channel.

Perhaps slightly wiser and more experienced than the first sergeant, the command sergeant major is expected to function completely without supervision. Like the old sage of times past, the command sergeant major's counsel is expected to be calm, settled and unequivocally accurate, but with an energy and enthusiasm that never wanes, even in the worst of times.

Assignable to any billets in the Army, the command sergeants major is all those things, and more, of each of the preceding grades of rank.

The sergeant major is generally the key enlisted member of staff elements at levels than higher than battalion. The sergeant major's experience and ability are equal to that of the command sergeant major, but the sphere of influence regarding leadership is generally limited to those directly under his charge.

http://www.armystudyguide.com/content/army_board_study_guide_topics/nco_duties/duties-of-an-nco.shtml

They keep troops off the grass.

At first my mind screamed "No don't answer, it's a trap!" You can read the book answers in the other responses. My experience with CSMs have shown them to generally be mentors, especially for the senior NCO's, as well as the person that takes the Commander's intent and distributes that energy among the unit and helps the other NCO leaders to ensure that their actions are in line with that intent.

Couldn't resist. A CSM does whatever needs doing, whenever it needs doing with a mixture of doctrinal enforcement and reality.
CSM is in reality probably the loosest defined leadership position going and I think it's that way for a reason. The CSM is like a free roaming radical in physics, roaming around and attaching itself to whatever needs fixing at the time.
I also think it depends on the Commanders.
My commanders basically turned me loose with some guidelines, -" make sure" PT and weight control is run rite, - Re-Up gets deserving Soldiers the best deals we can,- Training meets standards and takes into account the latest TTPs, - Safety, - Construction is done rite,- Equipment is maintained, -Counseling is done, -EEO, -Admin Flow. How I got that done and how much time I spent on each one was my business.
My schedule was basically: Come in talk to the Commander, Do PT, Eat at the mess hall and find a troop or group of troops to visit with, check one of the barracks on the way back and see the 1SG, go to the motor pool spot check someone doing maintenance or visit the mechanics, Check a training event or construction site, talk to the commander, Go to chow find different troops to talk to, Visit one of the staff sections or a different construction site/ training event, Move whatever admin stuff there was from my inbox to my out box, talk to the commander, Go home. Insert the inevitable meetings that occur in there anywhere but that's pretty much what I did. The BC, XO and I would each take a night to Come in on one of the nights between Friday and Sunday and roam the barracks to visit with Soldiers (note the emphasis on visit, not "FUCK WITH") We had a lot of troops with issues after the second deployment and roaming helped identify potential problems early so we could help not hammer. Our 1SGs and Company Commanders did the same.
I was blessed with four of the greatest BC's around and really liked the job and was able to help a lot of folks.
Long post but you asked

Here ya go, read this. Just go down to the bottom of the page; http://www.armystudyguide.com/content/army_board_study_guide_topics/nco_duties/duties-of-an-nco.shtml