Chaplets are prayer rules. Actually the rosary is a chaplet, the meditations which accompany the rosary give it special qualities other chaplets might not have (although you may add meditations to any chaplet).
You can create your own chaplet.
In the world a chaplet is most often a ring of jewels or flowers, or can be a ring of some other decorative material. (Commonly they are intended to be atop something, like on one’s head or at the top of a supporting column.) In the Faith then, a chaplet can be thought of as a ring of prayer, a nice analogy.
Chaplets are aften (or usually) named after some sainted person, but there is no guarantee that the person it is named for actually used the prayer rule themselves, the connection could be legendary or just another example of pious fiction. Sometimes the composer of the chaplet will name it after a favorite or appropriate saint as a dedication.
I do not know what the composition of the Chaplet of St Michael includes, I don’t recall having heard of it. My favorite chaplet is that of St Patrick, not because of some supposed connection to that historic person but because of the prayers included.