Witch

Witches are hostile, ranged mobs commonly spawning in Witch Huts. They're the second hostile ranged mob to spawn in the Overworld - the first being the skeleton.

Appearance

Witches have a similar appearance to the villager mob, and they wear purple and green robes with brown leggings underneath. They have large noses (which moves slowly around on the Witch's face, as stated in Dinnerbone's tweet) with a single wart and have lavender colored eyes. They wear the usual witch hat with a green buckle on it, and their skin is slightly paler than the normal villager. However, witches periodically give off purple star particles similar to the villager's green stars.

Combat

The witch mob uses splash potions of poison, weakness, damage, and slowness to fight the player. The current order of potions thrown is; slowness, poison, they will then proceed to throw potions of harming until the player is no longer poisoned which they will rectify by throwing another splash potion of poison and will continue to do this. The splash potion of harming will occasionally be substituted by potions of slowness. These potions will affect other mobs - not just the player. The witch does not burn in sunlight and when set on fire, drinks a potion of fire resistance. This can be seen when a bottle appears in the witch's hands. Iron Golems will attack witches as most other hostile mobs.
Witches are almost immune (85% damage resistance) to splash potions of poison and instant damage. When damaged, they will drink a potion of healing, healing themselves. When drinking a potion, a witch's nose will point straight forward (instead of down). While healing they can't attack the player. If lit on fire by lava or fire, witches will quickly drink potions of fire resistance, making lava and fire ineffective ways of killing witches.
A bow will likely be the best weapon for dealing with a witch, as the splash potions have only a short range (at most nine blocks) compared to arrows (which, when fired straight at full charge, travel 24 blocks). If a bow is not an option, however, a direct melee charge is the best option. Due to the witch's slow attack speed, if the player runs in a straight line and manages to get a quick sword strike in, the witch will try to heal themselves with a potion of healing, leaving the player to attack them without fear of retaliation.