Based on the question, I'm not sure if you're referring to the story "The Things They Carried" or the entire short story collection by the same name. I will focus mostly on the story and make some general comments about the collection to close.
The central idea of the titular story is that the soldiers in the Vietnam War carry a variety of "things," some literal some more abstract. For example, they carry equipment, rations, weapons, and the physical items they need to fight and to live. Beyond that, they carry items from home that have sentimental value. In a more abstract sense, they carry emotions, namely fear. They carry what they feel is the need to keep their emotions hidden, to act tough, to play the role of the typical soldier. However, their sentimental items and emotional attachments provide them a relief, an escape from their current reality. They can feel human when they feel linked to the world back home, even though they are so separate from it in so many ways.
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