Simplify the following text for a Grade 5 native English-speaking person.
Original: A hair iron or hair tong is a tool used to change the structure of the hair using heat . There are three general kinds : curling irons , used to make the hair curly , straightening irons , commonly called straighteners or flat irons , used to straighten the hair , and crimping irons , used to create crimps of the desired size in the hair .
Simplified: Ceramic hair irons are believed to be gentle to the hair .