Chemise's have been around for a long time; even the concept of one was used in medieval times. Styles changed depending on the time period.
The main job of the chemise was to protect the dress from sweat. Obviously they didn't have deodorant, so something to keep those ugly stains off the dress was a must.
Usually a woman (and girls too) owned many chemises; however long between wash days (once a week, maybe) might be the amount, plus a few. So about ten would be sufficient, maybe more. They were easy to change if one got too sweaty. They were also easy and cheap to make, being made out of cotton or linen. Any reenactor will tell you that you can never have too many!
This one is from 1870, but it looks similar to the ones from earlier.
This is one from 1790 -1810; because dresses in this era were so thin, a long chemise helped them be less see-through.
They could be decorated, or very plain. Because they weren't seen beneath, it didn't matter too much.