“Can someone explain what Maaravit And Yotzrot are?”
Piyuttim said in the birkas kiras shema and during the kiras hashatz. Sphardim don’t do it as they posken it’s a hefsek.
You’ll find them in most Ashkenazi Machzors even though ~100% of Ashkenaz-davening shuls/yeshivas in America have been mevatel the minhag on account of the Gra. Some do strictly on R”H and Yom Kippur, I believe.