Before the return of Macao, according to the laws at that time, people born in Macao could become Portuguese citizens (that is, hold Portuguese passports), so many Macao people held Portuguese passports.

After the return of Macao, according to the Basic Law of Macao, all China citizens who are permanent residents of the Macao Special Administrative Region and hold permanent identity cards of the Macao Special Administrative Region can apply for passports of the Macao Special Administrative Region regardless of whether they hold other passports or travel documents.

But not the other way around. A person who didn't have a Portuguese passport before now has a Macao SAR passport, but he still can't apply for a Portuguese passport (unless he marries a Portuguese passport holder).