How would you like to experience WordPress functions within your inbox on a daily basis? If so, consider signing up to the WordPress Daily Documentation site. Each day features a different function within WordPress sent to your inbox which contains examples, an explanation of what the function does, parameters, and the usual information you would find via other sources. Since signing up, I’ve received emails covering add_shortcode() and get_the_ID().
There are all sorts of ways to view information related to specific WordPress functions but this method may be especially useful to those who are starting to learn what functions are and which ones WordPress contains. But if you don’t feel like putting your email address on yet another subscription list, there is always the Codex.