They can't be the target of spells or abilities, their static abilities have no effect on the game, their triggered abilities can't trigger, they can't attack or block, and so on.

Phased out permanents are treated as though they don't exist.

Those Auras and Equipment will phase in at the same time that creature does, and they'll phase in still attached to that creature.

As a creature is phased out, Auras and Equipment attached to it also phase out at the same time.

Similarly, phasing in won't cause any “enters the battlefield” abilities to trigger.

Phasing out doesn't cause any “leaves the battlefield” abilities to trigger.

If they leave the game before their next untap step, it phases in as the next untap step begins after their turn would have begun.

If an opponent gains control of your nonblack creature, you phase it out with Divine Smite, and the duration of the control-change effect expires before it phases back in, your creature phases in under your control as that opponent's next untap step begins.'When darkness closes in around us, my blade will light our path.'

(If it phases out, treat it and anything attached to it as though they don't exist until its controller's next turn.) If that permanent is black, exile it instead. Target creature or planeswalker an opponent controls phases out.

Divine smite 5e