"He helps the birds."
Translation:Αυτός βοηθά τα πουλιά.
No difference in meaning.
βοηθά is the older, contracted form and may be slightly more formal; βοηθάει is the more "regular" form and may be slightly more informal.
But they both mean exactly the same thing. Perhaps a little bit like "do not" versus "don't" - they mean exactly the same thing as well, aren't completely interchangeable stylistically, but in practice it doesn't matter a great deal which one you use as a learner.
Does this rule apply to other verbs? Are αγαπά and αγαπάει both correct? Or περπατά/περπάτει?
Yes, this applies to αγαπά/αγαπάει and περπατά/περπάτει and other verbs as well.
Sorry, I meant to say that why were two of the options correct? Since I didn't write the other option down, I guess it makes hard for others to answer my question.
That's true. The options are chosen at random and so nobody knows what three sentences you were given.
But do note that it says "Mark ALL correct options" in multiple-choice questions.
Sometimes two options are correct; I've even seen questions where all three were correct.
Keeps you on your toes :)
Thanks for the info. I didn't realize the options were chosen at random, so I remember to write the example into my post when I have the problem. I didn't forget about the mark all the options setting, I just didn't understand all the options, which happens in the Greek course quite a bit. I usually have used Duolingo for romance languages, so I usually understood why another option would be correct.