Bootstrap is an open-source Javascript framework developed by the team at Twitter. It is a combination of HTML, CSS, and Javascript code designed to help build user interface components. Bootstrap was also programmed to support both HTML5 and CSS3. Also it is called Front-end-framework. Bootstrap is a free collection of tools for creating a websites and web applications. It contains HTML and CSS-based design templates for typography, forms, buttons, navigation and other interface components, as well as optional JavaScript extensions. Some Reasons for programmers preferred Bootstrap Framework Easy to get started Great grid system Base styling for most HTML elements(Typography,Code,Tables,Forms,Buttons,Images,Icons) Extensive list of components Bundled Javascript plugins

摘自About Bootstrap Framework

引导最流行的HTML, CSS和JS框架来开发响应式的，移动优先的web项目。它是非常流行的开源工具包。非常容易使用它的造型。最新版本是bootstrap 4。bootstrap具有Sass变量和mixins，响应式网格系统，广泛的预构建组件和强大的JavaScript插件。 现在他们为React Js、Angular和Vue指定了他们的工具包

Bootstrap主页 Vue引导 角引导 引导的反应

它是一个HTML、CSS和JavaScript开源框架(最初由Twitter创建)，您可以使用它作为创建网站或web应用程序的基础。

更多信息和下载链接 开始 例子 主题 引导-引导编辑器和生成器

更新

官方引导网站更新，包括一个明确的定义。

Bootstrap是最流行的HTML、CSS和JS框架，用于开发响应式、移动优先的web项目。”

“由@mdo和@fat用全世界所有的爱设计和建造。”

Bootstrap is an open-source Javascript framework developed by the team at Twitter. It is a combination of HTML, CSS, and Javascript code designed to help build user interface components. Bootstrap was also programmed to support both HTML5 and CSS3. Also it is called Front-end-framework. Bootstrap is a free collection of tools for creating a websites and web applications. It contains HTML and CSS-based design templates for typography, forms, buttons, navigation and other interface components, as well as optional JavaScript extensions. Some Reasons for programmers preferred Bootstrap Framework Easy to get started Great grid system Base styling for most HTML elements(Typography,Code,Tables,Forms,Buttons,Images,Icons) Extensive list of components Bundled Javascript plugins

摘自About Bootstrap Framework

据我所知，Bootstrap是一个定义良好的CSS。虽然使用Bootstrap，你也可以使用JavaScript, jQuery等。但主要的区别是，使用Bootstrap，您可以只调用类名，然后在HTML表单上获得输出。如。按钮的着色，文本的塑造，使用布局。对于所有这些，您不必编写CSS文件，而只需使用正确的类名来塑造您的HTML表单。

简单地说，Bootstrap可以理解为一个前端web框架，它是由Twitter创建的，用于更快地创建设备响应式web应用程序。Bootstrap也可以主要理解为定义在其中的CSS类的集合，可以简单地直接使用。它利用CSS, javascript, jQuery等在后台为Bootstrap元素创建样式，效果和动作。

You might know that we use CSS for styling webpage elements and create classes and assign classes to webpage elements to apply the style to them. Bootstrap here makes the designing simpler since we only have to include Bootstrap files and mention Bootstrap's predefined class names for our webpage elements and they will be styled automatically through Bootstrap. Through this, we get rid of writing our own CSS classes to style webpage elements. Most importantly Bootstrap is designed in such a way that makes your website device responsive and that is the main purpose of it. Other alternates for Bootstrap could be - Foundation, Materialize etc. frameworks.

Bootstrap让你从编写大量的CSS代码中解脱出来，它也节省了你在设计网页上花费的时间。