Snippets - Common code templates
Speed up the creation of common blocks of code using snippets, an easy to define text template system provided by the Emacs package called yasnippets
YASnippet comes with a number of mode-specific snippets that expand to anything from a simple text replacement to a code block structure that allows you to skip through parameters and other sections of the code block.
For example, in html-mode typing div and pressing M-/ expands to <div id=" " class=" "> </div> and places the cursor so you can type the id name. Press TAB to move the cursor through the other sections, i.e. the class name and the contents of the div.
Many programming language layers come with their own pre-defined snippets and there are snippet commands for creating your own.
Snippet expand keybinding
To expand a snippet simply type its name and press M-/.
Snippets in Auto-completion popups
You can include yasnippets in the autocompletion popup menus too.
Resources
For more examples on where snippets are useful, read Sacha Chua's article on {how to make better use of Yasnippet in my Emacs workflow}(http://sachachua.com/blog/2015/01/thinking-make-better-use-yasnippet-emacs-workflow/)