A Korean friend kindly showed me the difference... 어 is made quite close to the back of the mouth, like the o in Korean. It's usually transliterated as "eo", as in Seoul (서울). 오 is pushed forward to the lips, as in show. 여 and 요 just add a y sound, of course.

it's just different characters. you could say both is read "yo" but there's a significant difference as 여 is a "lighter" sound and 요 is maybe "heavier" and even almost like a "yu". same goes with 어 and 오 (o) it's nest for you to learn to differenciate it by listening to a native speaking! maybe try to find a video of basic hangul on youtube and pay attention to the difference in sound.

ㅕ - sounds as "jo", but you have to open your mouth as for saying "a". This sounds is something between "jo" and "ja" ㅛ - sounds just as "jo". Oh, and when you see "요" in the end of the sentence, it means that it is in a polite form (informal and the most using). 저는 여자에요. 괜찮아요. 도와 주세요:)