Tagalog is the first language of the Philippines and spoken by 98% of the Filipino people. It is the first language in the National Capital Region, the main cities in the country's capital as well as nearby provinces in Central Luzon (red in the map). Almost everyone in the Philippines understand Tagalog although a very small percentage cannot speak the language.
The official name of Tagalog is really Filipino (language). Note that the people in the Philippines are also called Filipino. In the following discussion, Filipino will refer to language.