Two of the most common result complements in Chinese are 到 () and 见 (). On this page we're only going to be talking about verbs related to the senses ("see," "hear," etc.), and for this usage, the two are interchangeable.
Result complements are a huge topic in Chinese grammar, but you can approach them in stages. The structure you come across the most is a verb with 到 ():
Subj. + Verb + 到 + Obj.
What 到 () does is indicate that the outcome of the verb is achieved - what its result is. Without a result complement, the sentence would describe only the action itself. To illustrate, 看 () "to look" is the action of turning your head in a particular direction and focusing your eyes, whereas 看到 (), "to see," is the result of your brain taking in the visual input. It may sound a little hokey, but it really is possible to "look but not see," and Chinese makes a clear distinction between the action and the result.
The complement 见 () is very similar to 到 (), and it is used in the same way:
Subj. + Verb + 见 + Obj.
However, there is a difference. 见 () is generally only used after verbs involving one of the senses, like 听 () and 看 (), whereas 到 () can be attached to a large variety of verbs, which we will discuss at a higher level later.
Subj. + 没 + Verb + 到 / 见 + Obj.
This structure can be negated using 没 () on 没有 (). This is because if there is a result, then it already happened. And you need to use 没 (méi) to negate past events, not 不 ().