Altogether is an adverb that modifies adjectives. Altogether can mean "entirely" or "completely," "all told," or "on the whole."
The bride was altogether unhappy with the flower selection.
Over the years he owned five cars altogether.
The performance was altogether pretty good.
There is also a slang expression, "in the altogether," meaning "naked."
All together means "all in one place."
Stand all together for the photo.