British English speakers use "biscuit" for sweet/salty crunchy snack (like a wafer) AND they use "cookie" specifically for the chewy baked kind like chocolate chip cookies. American English speakers use "cookie" for both sweet crunchy snacks and chewy baked ones, BUT they use "cracker" for the salty crunchy snacks.
Biscoito, bolacha=Cookie, biscuit (UK, Au, NZ, SF etc)
Pãozinho biscuit, pão/pãozinho americano biscuit or scone=American biscuit, savoury scone.
But unfortunately American biscuits aren't really known by the majority of people in Brazil, so you'll have to explain to them what kind of food you're talking about if they don't understand those terms above.
Cookie is a generic American term for a biscuit. In English a specific type of biscuit is a cookie, all other biscuits are generically called biscuits. Even a cookie can be referred to as a biscuit. If for example you had a varied selection of biscuits that contained the specific type the British call cookies, the selection would still only be referred to a biscuits, as in "Would you like a biscuit?" when referring to them all.
In English, there are often almost-synonym, one from the Germanic roots, and one from the French roots. Here, the etymology says:
"Cookie" is from Dutch "koekje", meaning "little cake" (also "koek" and "koke"), so it's a cognate of "cake" (And "cake" is a cognate of "cook" obviously)
And "Biscuit" is from French "biscuit", composed of "bis" (meaning "twice" in Latin) and "cuit" meaning "cooked"in French. A "biscuit" was in French originally a cookie cooked twice. It was originally the biscuits of the sailors. They cooked them twice, the first time to preserve the dought, and the second time before eating them.
In French, we don't make a distinction, all biscuits are "biscuits", and everything bigger than a "biscuit" is a "gâteau" (a "cake"), we call a "cookie" only the American chocolate chip cookie.