Result complements "-dao" and "-jian"

到 and 见 mark that a perception or a search actually succeeded.

Verb + 到 / 见

How it works

听到了吗? — did you hear it? Not "were you listening" but "did the sound reach you". Same for 看到 (saw), 找到 (found), 买到 (managed to buy).

见 does much the same with the senses: 看见, 听见. In practice 到 and 见 are interchangeable there, with 见 slightly more colloquial.

到 also covers reaching a target more generally: 想到 (think of), 收到 (receive).