What is the difference between a sermon and a speech? (Explain)

A sermon is a talk on a religious or moral subject, especially one given during a church service and based on a passage from the Bible. (Jesus talks, e. g)

A speech is human vocal communication using language. (It could be similar towards Martin Luther King and his speech which changed the world.)

As nouns the difference between speech and sermon

is that speech is (label) the faculty of uttering articulate sounds or words; the ability to speak or to use vocalizations to communicate while sermon is religious discourse; a written or spoken address on a religious or moral matter.