Minification is a procedure run on code text files that can reduce the text size by removing white space and substituting common values or names with shorter versions. Minification also offers the additional value of making code much harder to read and reverse engineer by third parties. It is best practice to minify any exposed JS and CSS Files before publishing them to a live site.
Minification can be done automatically through some development tools and website build procedures, or through minification CMS Plugins, or manually through minification tools available online.