The word for the form of the verb there -- "used" and "given" in your examples -- is "past participle". Those examples are of "passive" constructions, which typically use a form of the verb "be" -- "is" in your examples -- together with a past participle to make the "target" of the verb the subject rather than the object they would be in an active construction. You can't just reverse them; you have to change the form of the verb and the "by" clause, if any, becomes the subject. For example, the passive sentence "That is used for cooking by Indians" corresponds to the active sentence "Indians use that for cooking". If there is no "by" clause, you have to make something up, thus "That is used for cooking" can be recast as, for example, "People use that for cooking".