Think of a coloring book, but made of fabric and big enough to cover your lap on the couch. Most models measure around 59 x 50 inches and come with a set of markers in the box.
You pick a section, color it, and come back to it another evening. Because the blanket is wide, two or three people can work on it at the same time.
Patterns range from flowers and fruit to cats, food or retro game themes. A busy pattern keeps you going for weeks, while a simple one can be finished in a few evenings.
What makes these blankets different is the washable ink. Washable markers use water-based ink that, per the manufacturer, washes out in the machine, so you can start over. Check the care label before the first wash.
Some people switch to permanent fabric markers for a finished blanket they want to keep as it is. It helps to decide before you start which parts should be permanent.
Two small tips before you start. Color on a flat surface so the fabric does not stretch, and close the markers after each session so they do not dry out. Start with lighter colors; darker ones are easier to add on top than to take away.
Many adults treat it as a relaxing hobby, something to do with their hands while talking or listening to music. As a gift, it works for people who like crafts but already have plenty of coloring books.