Some simple examples of the questions it attempts to answer are:
Behavioral ecology is closely allied with ethology, but the latter tends to focus more on the physiological and genetic mechanisms by which behavior is regulated.
Before about 1980, behavioral ecology and sociobiology were more or less synonyms. However, attempts to apply theories of the evolution of animal behavior to human beings became very controversial. Since these attempts were closely associated with the sociobiology term, most workers in the field nowadays prefer to use the term behavioral ecology for the less controversial application of these ideas to animals in general.
(These two are respectively first/second college year level, and third/fourth college year level)