A script kiddie is a hacker, often a young amateur, who uses scripts and programs written by others instead of developing their own. Script kiddies lack the knowledge to understand the details of how the tools and exploits they use work, relying on software written by others and distributed online. Script kiddies often perform their attacks for excitement and notoriety instead of for financial gain or access to specific systems.
Experienced hackers tailor their attacks to a specific system and hope to prevent the victim from discovering the hack. Script kiddies using pre-made tools lack the experience to adjust their attacks to the targeted system and lack the knowledge to cover their tracks if the hack is successful. Their hacking attempts are often indiscriminate and targeted at any vulnerable system they can find, instead of deliberately focusing on a particular system. However, a script kiddie pulling off a successful attack can still cause significant damage.
Certain types of hacks are most common amongst script kiddies due to the relative ease of the attack and the availability of tools online. DDoS attacks, for example, don't require advanced skills to carry out, and many pre-made tools are readily available. Website defacement is also a common script kiddie attack, where one gains access to a web server and modifies a webpage to brag or to make a statement. Finally, while script kiddies lack advanced hacking skills, many are familiar enough with HTML and web development to create convincing fake websites for phishing attempts. After all, the easiest way for a script kiddie to gain access to a system is for them to steal a username and password to it.