1) Removes residue from the skin.
After cleansing there may still be cleanser, dirt and grime residue on the skin.
2) Helps close, tighten and refine pores.
Generally speak pores cannot be shrunken however using a cold product on the skin like toner helps tighten skin.
3) Disinfects the skin.
Especially if your toner contains an antibacterial essential oil.
4) Hydrates the skin.
Used under a moisturiser, the oils and butters in the moisturiser help lock the toner in, “Lock it in Eddie”, which hydrates the skin.