My English is poor. I hope you can understand my explanation。 看到 stress action have result or achieve aim 我看到你 I saw you. 你看到什么？what did you see 看 stress where line of sight 看书 read book 看电视 watch TV 你在看什么？What are you looking at

Many thanks Eric !

Hi Luciana: 看(kan4) just means look (just an action) same words:瞧(qiao2) 看到(kan4 dao4) meaning see something (see what you look) same words:看见(kan4 jian4)，瞧见(qiao2 jian4) for example：看！就在那里，你看到了吗？ (kan4! jiu4 zai4 na4 li3, ni3 kan4 dao4 le1 ma1?) Look! over there, did you see that? hope could help you

I think "到" is similar to preposition in english. Examples: 看到 看见 看望 看出 看来 看去

kan is an action.kan means look .e.g. Look, the boy is singing. 看，那个男孩正在唱歌。强调让你注意这件事。 kan dao is a result. For exapmle. I saw you in the classroom yesterday.昨天我看到你在教室。 强调你是在教室，不是在其他地方。kan dao emphasizes you were in the calssroom ,not other places.