NGC281 - the Pacman Nebula is a comparatively bright HII emission nebula in the constellation of Cassiopia. At it's heart lies the small open star cluster (IC 1590) which ionises the surrounding hydrogen gas & results in the red glow.
The 'mouth' of the pacman, is caused by large amounts of dust which obscure & attenuate the visible emission from the nebula.
Also visible in the nebula are several Bok globules, which consist of isolated & relatively small regions of dense cosmic dust and gas, typically with a mass of 2 to 50 solar masses.
NGC281 is estimated to be about 9,200 light years away and is about 48 light-years across.
For more info. see the Wikipedia entry.