层理论简介

摘要：

简要介绍层的基本内容，然后对预层、丛、流形和奇点进行相关评论，旨在指出它们的差异不仅在于它们不同的形式数学结构，而且在于它们最初引入的目的。

英文摘要：

Essentials of sheaves are briefly presented, followed by related comments on presheaves, bundles, manifolds and singularities, aiming to point to their differences not only in their different formal mathematical structures, but also in the very purposes for which they were introduced in the first place.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。