So, for example, in the sentence,
George Clooney is a total angel.
The tenor of this metaphor is "George Clooney," while the vehicle is "angel."
Here's another example:
I devoured the latest Hunger Games book.
The tenor of this metaphor is "reading" (a word not used here) and the vehicle is "devoured." Sometimes, writers can get all tricky and use a tenor that's not actually in the sentence, but the effect remains the same. In this case, reading is like eating—devouring, to be exact.