Please enlighten us non-Mormon exposure types.
Wards? Some organizing unit from the context. Are they voluntary, like picking a specific church, or preset, like parishes?
My experience with mormonISM, is that nothing is voluntary.
The leaders tell you where you can go or not go.
In established areas a ward will have somewhere around 250-300 people attending the service. Outside of Utah, California, and Idaho a ward may be closer to about 200 attending.
A group of wards are organized into a "Stake." Typically around 10-12 wards, but I have seen as little as 7 and as many as 20. Many stakes are organized into "areas." The next organization above areas is the church as a whole. In even less populated areas you can have branches (tiny wards, sometimes as few as one family) and missions (sort of an "area").
While you are not required to attend the ward you live in, there is a downside to not doing so. The LDS church has no paid ministry at the local level (and at the top levels only an "allowance/travel stipend" payment to cover costs). The ward is lead by a bishop who is "called" to serve as such by stake leadership. And nearly every attending adult has a "calling" that helps staff the ward. Everything from Sunday school teacher to organist to scoutmaster is filled by attending members. You don't campaign for assignments in the ward. The situation is that you can only have a calling in the ward you are assigned. If you attend a ward that you do not live in, you cannot be given a calling. Some may consider this a good thing.
There are special cases where the boundaries overlap. A stake might have a "spanish ward" or "deaf branch" that draws people from the entire stake (or other similar language or condition group). In Utah there are branches set up at nursing homes. I know of cases where two stakes share a spanish ward.
Another special unit is the "singles" ward or branch. In the LDS church those between 18-30 and unmarried have a special program called "young single adults" that involves special activities and such. And in some areas they set up a ward for these folks. For a long time these wards were open to anyone living anywhere, so the more dynamic wards grew, and in a compounding way as the "dull" wards died because everyone was going everywhere else.
In colleges with high LDS populations (like BYU) they used to set up student wards, which were much like a singles ward. And it appears that the church has changed the way they organize these wards. Not being in Utah, I do not know the details on all the differences. Since they still end up having to divvy up the population into manageable congregations, it really doesn't matter if they call it a student ward or a singles ward. You are still going to end up breaking the on-campus dorms (which tend to be unmarried folks) into groups of 300 or so students.
Hope this helps. Let me know if more detail is desired.
Wards are congregations. You are assigned a ward based upon your address (ward boundaries). You cannot attend another ward for any real length of time without a very good reason and permission from your Bishop. In some ways they are more restrictive than parishes even.
BYU students who live at home had the choice of attending a student (or singles) ward or a “family ward” (the same ones with their parents.
Singles living on their own could attend (with permission) a singles ward or a ‘family ward’ but if they were young enough (mid 20’s) were encouraged to attend a singles ward to find a mate.
Married couples and older singles (over the age of 30 or 35) attended ‘family wards’. Again, you had to decide and get permission if you were to attend outside your ‘ward boundaries’.
I attended a Student ward when I was in BYU housing. When I moved to BYU approved housing (with a friend’s aunt - who had to go through a whole approval process) I attended the family ward with her. Her niece, my roommate, attended a singles ward down a block. But we all had to get approval to do so.