CSS Max-width is a CSS property that allows you to set the maximum width of an element. It can be used to prevent elements from becoming too wide on larger screens, or to limit the size of an element on smaller screens. It is an important tool for creating responsive designs that look
From Wikipedia
Cascading Style Sheets (CSS) is a style sheet language used for specifying the presentation and styling of a document written in a markup language, such as HTML or XML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.