When you use during, you are usually emphasizing that something is continuous or repeated. You can also use during to say that something happens while an activity takes place. I met a lot of celebrities during my years as a journalist. During her visit, the Queen will also open the new hospital.
During means throughout the entire time or at a certain point in time when something was happening. During is a preposition, which is a type of word used before a noun or pronoun to relate it to another part of the sentence, especially to express a relationship based on space or time.