Macau used to be a colony of Portugal many years ago. When Portugal ruled Macau, they had a military to help keep their colony safe and protected. Just like the police help keep your neighborhood safe, the military helped to keep Macau safe.
The Portuguese military in Macau had soldiers who wore special uniforms and carried weapons like guns and swords. They would practice their fighting skills and work together to make sure they were ready to defend Macau if anything bad happened.
The military also helped with important ceremonies and events. They would march in parades and do demonstrations of their skills for visitors to see.
Overall, the military in Macau under Portuguese rule was there to help protect the people and keep their colony safe.