By telling the reader what the character is like
<u>Identify the present participle in the sentence.</u>
The cars<u> passing by</u> are filled with commuters.
The present participle form is formed by the verb + ing, and its use depends on its placement.
In the case of the provided sentence, the verb would be "pass"+ing = <em>"passing"</em>. Furthermore, the present participle in the sentence has the function of a <u>verbal noun</u>: <em>"the cars passing by".</em>
