From the Monster Hunter World Wiki
Kinsect is a special equipment in Monster Hunter World (MHW) that players choosing to use the Insect Glaive can wield. It gives the user bonuses such as more damage, faster movement and better defense. Kinsects also have their own attacks and damage types, that vary from Kinsect to Kinsect. Kinsects can also be upgraded, much the way Weapons are and have their own upgrade trees.