Kurds are an ethnic group similar to any other, like Turkmens, or Bengalis, or Japanese etc. Kurds are part of the group of people that speak Iranian languages, that includes Persian, Kurdish, Pasto, Balochi, and a bunch of other ancient languages. Turks on the other hand, are part of the group that speaks Turkic languages, including Turkish, Azeri, Kazakh, Uzbek, Turkmen, Kyrgiz. Most of the Turkic people live in central Asia, while the Anatolian Turks settled here sometime in the middle ages. So yes, Turks and Kurds are very different.
The Kurds live in the region at the center of Anatolia (proper Turkey), Persia, Arabia, and the Caucasus mountains. They are mainly between 30 and 32 million. Because of their location, and European division of the Ottoman empire, they were divided into many nations such as Syria, Iraq, etc. So now, with the rise of nationalism, there are massive independence movements that include the PKK.
Kurds are majorly Muslim, and often pride themselves in saying that, "Compared to the unbeliever, the Kurd is a Muslim".
Hope that helped, I love reading about ethnic and linguistic groups.
PS: Saladin Ayyubi was a Kurd.