During means throughout the time something is happening, or at some point within that time. If you read a book during summer vacation, you read it sometime while summer vacation was going on. If it rained during the baseball game, rain fell while the game was being played.

The word helps us place one event inside the timeframe of another. You might eat lunch during your school day, practice piano during the afternoon, or see shooting stars during the night. Sometimes it means the whole period: “I stayed focused during the entire test.” Other times it means just part of that period: “I coughed during the concert” (you didn't cough the whole time, just at some point while it was happening).

During always needs to be followed by a noun or noun phrase describing a time period, like “during recess” or “during the 1800s.” You can't say “during I was walking” (that would be “while I was walking”). Think of during as answering the question “when?” by pointing to a stretch of time and saying “somewhere in there.”