Hiragana「お」and「を」actually make exactly the same sound. But they are typed out differently on keyboard. To make the first hiragana, simply type “o”, to make the second hiragana, “wo” need to be typed. Also, some textbooks present them differently in order to avoid confusing students. However, some textbooks present them the same, both as “o”. The rule I always teach my students is that when hiragana “o” is used as a part of a vocabulary, e.g. おいしい oishii (then it is the hiragana お. However, when it is used as a particle, it is always を. For example, すしをたべます (I eat sushi).
