A 2 in 1 hair straightener brush is a hair styling tool that combines the functionality of a hair straightener and a hairbrush. It is designed to straighten hair while brushing it at the same time, making it a convenient and versatile tool for styling hair. The brush typically has a heating element built into it, which allows it to straighten hair as it glides through the strands. The bristles of the brush are usually made from ceramic or tourmaline, which helps to distribute heat evenly and reduce frizz.