بسم الله الرحمن الرحيم الحمد لله رب العالمين والصلاة والسلام على سيدنا نبينا محمد وعلى آله وصحبه أجمعين اما بعد

َQuestion: What is the difference between shirk and kufr?
Answer: All Shirk is called kufr; invoking anyone other than Allah, seeking help from anyone other than Allah, worshipping anyone other than Allah is called Shirk, and is also called Kufr. It is also called Kufr and Shirk when a person denies the obligation of Salah, or claims that Zina is Halal, is called a Kafir and a Mushrik. However, mainly a person who denies a religious obligation or a prohibited matter is called a Kafir. whereas a person who invokes anyone other than Allah, or seeks other than Allah’s help, or vows to anyone other than Allah is called a Mushrik. Otherwise, all Shirk is Kufr, and all major Kufr is called Shirk

Sheikh Abdul-Aziz bin Baz

Source:

https://binbaz.org.sa/fatwas/12850/الفرق-بين-الشرك-والكفر#:~:text=كل شرك يسمى كفرًا، كل,كانت الدعوة لغير الله، الاستغاثة