I have an assignment that requires me to go to a local government office where real property records are maintained and locate a deed that has

I have an assignment that requires me to go to a local government office where real property records are maintained and locate a deed that has recently been filed and that also is subject to a mortgage or deed of trust. It is 2 different documents. I don't know how I'm missing it in my textbook but I do not understand what kind of document he means by "subject to a mortgage or deed of trust". I don't know how to locate the second document he is referring to.