Gringas are a variety of tacos which uses as a base a quesadilla

Quesadilla

A quesadilla is a flour or corn tortilla filled with a savoury mixture containing cheese and other ingredients, then folded in half to form a half-moon shape. This dish originated in Mexico, and the name is derived from the Spanish word queso ....

, consisting of a flour tortilla

Tortilla

In Mexico and Central America, a tortilla is a type of thin, unleavened flat bread, made from finely ground maize...

 filled with cheese (quesadilla) and "al pastor" meat, topped with cheese. This is then grilled in the same manner as a quesadilla. Some say the name appears to come from the dark spots that appear on the white surface of flour tortillas when heated, that resemble of freckles in white skin, a "gringa" skin. In general, the name was established from the idea that (wheat) flour tortillas are preferred north of the border. Las pochas is the name given to another variation of tacos made in the same manner, but instead of wheat flour tortillas, corn tortillas are used and instead of "al pastor" meat, grilled meat, pork or less frequently beef is used.

In addition, the term "gringa" can be used as a slang reference to an Caucasian (white) American female; hence, gringas is the plural form.