When people communicate the sentences they use are usually phrased conceptually rather than concretely.
For example, when Pilot X describes how his co-pilot and himself fly their plane by "keeping the plane under control", the phrase "keeping the plane under control" describes a series of events. Notice though, the only word in the phrase which directly signifies an object is "plane". The rest of the words signify concepts. For now, we can ignore the word "the" since it modifies the word "plane" and nothing else; which leaves the words "keeping", "under" and "control" respectively. Thinking about each word individually doesn't signify the intended message the pilot was trying to convey at all. There is nothing concrete--no objects--located underneath "control"; the word "control" doesn't even signify an object in the first place. Only when you think about the phrase as a whole does the meaning become clear.
If we rewrote the pilot's original phrase ("keeping the plane under control") using words which directly signified all the objects the pilot was attempting to talk about, the result would be a lengthy paragraph. It's much easier, for the pilot and for us, to talk about events using words that signify concepts. Concepts are groups of words which describe objects in relation to other objects; descriptions which commonly include words that signify other concepts. For example, the word "democracy" signifies a concept; most descriptions of "democracy" use words that signify other concepts (e.g. describing "democracy" as a "form of government" uses the words "form" and "government", both of which are words that signify concepts). Unfortunately, hearing statements which use words that signify concepts without correctly identifying the objects those words are intended to signify is misinterpreting the meaning of the statement heard.
If a person misinterprets something you've said, unless one of you notices the misinterpretation has occurred, the person will continue to assume they correctly understood what you meant.

Sharks ate my homework.