Computers are very important because we work with them, and we keep our secret folders and files in them.

folders 是 folder 的复数形式，folder 由动词 fold（折叠）加后缀 -er 构成，原指"可以折叠的物品"。在电脑术语中，folder 指用于分类存储文件的"文件夹"，就像现实中用来整理文件的折叠夹一样。