What is a lye for food recipes?

i'm from philippines and i like searching for pinoy delicacies recipe and want to try it at home.but some of the recipes have lye or 'lihiya' ingredient.i'm wondering what lye is.could anyone tell me something about it and were could i find it?What is a lye for food recipes?
Lye or Lye water in Asian cooking is used as both a preservative and it breaks down hard fibers, as the lye opens up the fibers to allow them to cook, and you do not cook thing in lye, but soak them or treat them to soften them before cooking and you rinse off the the lye.





In Chinese cooking like dumplings and steamed pastrys, it is used with the leavening agents to add extra lift, the also call it alkali water, it along with ammonium carbonate are used add crispness or again soften the dough and then add a protect coating with steamed dumpling to keep them from getting soggy.





Lye can be found in most grocery store in the cleaning agent aisle, now in the Phillipines, I am not sure, if you can not find the powder one used for cleaning sink drain and this is very corrosive, I would seek out the lye or alkali water from a Chinese grocery store, with the baking ingredients, it is in a small glass bottle.