What are the dimensions and measurements and size of a twin comforter?

A typical twin size mattress is 38" x 75" so a twin comforter will be larger than this by several inches in both length and width. There is variety with different manufacturers, etc. But this is the minimum that a comforter could be to fit on the mattress Comforter sizes vary slightly from manufacturer to manufacturer, but generally they are about: Twin 68"x 86" to 92" long

Full 80"x 90" Full/Queen 88"x 88"

Queen 86"x 94"

King 110"x 96" Twin and Full sizes in particular vary considerably in length and slightly in width. This may be to accommodate twin XL mattresses or just taller teens and adults in full size beds, or to cut costs on a cheaper blankets.