Perlite is made from volcanic rock that has been heated really quickly causing the water in it to soften the rock, making it expand. It turns into very light pebbles that are mixed into potting mixes and soils.
Perlite is combined with coco peat when making a mix for growing cuttings and seeds. It helps to make sure that the mix drains properly because if it doesn’t, the new roots might rot.
SMARTY TIP: Before opening a bag of perlite, make a small hole and pour in some water and smoosh it all around. This will stop it from being so dusty when you do open it.