Monsters throughout Wraeclast won't just hurt you -- they can also inflict ailments. Fortunately, you can too.
Ailments usually come from a specific kind of damage. Fire damage can 'Ignite', which deals further fire damage over time. Cold damage can 'Chill', slowing you down, or 'Freeze', causing you to stop moving entirely. Lightning damage can 'Shock', causing you to take a lot of extra damage from any source. Some enemies can also 'Poison' you or inflict 'Bleeding', both of which deal damage over time. If you move while you're bleeding, the bleeding will deal extra damage.
Dealing with Ailments:
Items, passive skills, support and skill gems, curses, and other things can each influence how likely it is that you'll suffer or inflict any of these ailments, as well as how effective these ailments are.
Flasks are capable of removing each ailment if they have the right mods. Figuring out which ailments might be dangerous to you and getting flasks that will remove them can make a big difference to your journey.