Tapioca sheets are used as wrappers for Thai and Vietnamese spring rolls. The grid pattern on the sheets is created by the bamboo mats used to dry the sheets. Tapioca sheets come in rounds, squares and 1/4 rounds. To use, soften the sheets one at a time in water. It takes 1 - 2 minutes to become pliable. Lay the moist sheet on a smooth surface, top with fillings and roll up. Slice in half on the diagonal. This type of wrap can be made up to 6 hours ahead.
Tapioca sheets / spring roll wrappers can sometimes be purchased with seeds, such as sesame seeds embedded within the wrapper.
Some brands of "rice paper wrappers" are made from tapioca flour (starch) rather than rice paper. The tapioca sheets are slightly "more strechy" than true rice paper wrappers. Both are used for spring rolls including fresh rolls and summer rolls. Many times all of these sheets are simply labeled at Spring Roll Wrappers.
You can find these sheets in most any Asian market. You can buy these as Spring Roll Wrappers from a variety of sellers on Amazon.com: Spring Roll Wrappers. Please not that there are about 25 sheets per package (may vary per brand). Some sellers sell multiple packs.