Original: The term PAL is often used informally to refer to a 625-line/50 Hz (576i), television system, and to differentiate from a 525-line/60 Hz (480i) NTSC system.
Simplified: The term PAL is often used informally to refer to a 625-line/50 Hz (576i, principally European) television system, and to tell it apart from a 525-line/60 Hz (480i, principally North American/Central American/Japanese) NTSC system.