What is the difference between a disbeliever (kafir) and one who associates partners with God (mushrik)?

The difference between a disbeliever (kafir) and an idolater (mushrik) stems from the difference between disbelief (kufr) and idolatry (shirk). They may sometimes be used interchangeably, both referring to disbelief in God Almighty. However, a distinction can also be made, where shirk specifically refers to the worship of idols and other creatures, even while acknowledging God Almighty, as was the case with the disbelievers of Quraysh. In this sense, kufr is a broader term than shirk.