1. Definition difference: PNJ refers to "Phong NHA-Kebangna National Park", which is a national park in central Vietnam, a world natural heritage and a world geological park. MLB refers to "MajorLeagueBaseball", which is the top professional baseball league in the United States and Canada, and consists of 30 teams.

2. Domain differences: PNJ is a geographical concept, which refers to parks, mainly involving nature protection and tourism. MLB is a concept in the field of sports, involving professional baseball games and athletes. It is the top professional baseball league in the United States and Canada, attracting many baseball fans and professional athletes.