"Él ayuda al hombre."
Why is it "al hombre" and not "el hombre"?
"Al" is "to the" but the sentence doesn't sound correct when translated like that
This is called the personal "a". In Spanish, when the direct object is a person, it is preceded by the preposition "a." This word has no English translation. (See http://www.studyspanish.com/lessons/persa.htm for further explanation)
It'd be nice if Duolingo would explain this somewhere, as I didn't figure it out either until someone explained it to me in one of these discussion sessions.