Using snippets saves you time typing common coding structures and helps you avoid silly typos too. Simply typing in a snippet name and pressing
M-/ or using
M-x yas-expand gives you the full text & code structure from the snippet template.
For example, if you are defining a new function in Clojure then type
defn and press
M-/ to expand to the full definition structure, including all parens. Then use
TAB to move through the structure to complete the name, doc-string, arguments and behaviour of the function.
Lets look at the built-in snippets that come with the Clojure layer in Spacemacs (and should be the default in Emacs YASnippet package).