work at vs work on

work at and work on both are verbs.

Word	Noun	Adjective	Verb	Adverb
work at	No	No	Yes	No
work on	No	No	Yes	No

As verbs, work at and work on are synonyms defined as:

work at and work on: to exert effort in order to do, make, or perform something

work at (verb)	work on (verb)
to exert effort in order to do, make, or perform something	shape, form, or improve a material
	to exert effort in order to do, make, or perform something