While developing a module or modifying a template in Drupal you'll often print variables, especially if you're in a preprocess hook.

You learn early on how to use var_dump and print_r function. But these functions can sometimes display too much information and can be hard to filter through the arrays or methods in the variable.

In Drupal 7, with the Devel module, you could use the dpm or dsm function. When used, these functions will print variables at the top of the page or in the message area using Krumo.

Now in Drupal 8, Devel has adopted a new library to print variables and it's called Kint.