It is basically minified css and JS file to use less space that being loaded by our application
Bundling and minification are two techniques you can use in ASP.NET 4.5 to improve request load time. Bundling and minification improves load time by reducing the number of requests to the server and reducing the size of requested assets (such as CSS and JavaScript.)
Bundling and minification techniques are used to improve request load time by reducing number of request to the server. Bundling combines multiple file into single file like CSS, javascript. Fewer files means fewer request ultimately improves load performance. Minification is the removal of unnecessary things for code optimzation like white space,comments etc.
Bundling is the concept where we group files i.e css, js files, and request to the server in a single attempt. Bundling helps to overcome load from the server that happen in case of individual request.Saves bandwidth and load application faster.Minification : In manification, we remove extra spaces from js files,remove commented lines to lower the size of the js files that helps us to load js file fasters.
Bundling means grouping of same type of file in a single unit.Minification means removing extra space, multilines and comments from .js or .css so that file size should be reduced which will take less time to load.