Some records are defined as scripts, in that running a script is their primary function. An example of this type of script might be a script includes or UI script. Other records, such as business rules, will support scripting if you enable the Advanced view, but have more basic functionality even without scripting. What might be less intuitive, is that certain fields such as the condition builder, can also support scripting if the script is invoked using the javascript: keyword (including the trailing colon).
Later, we'll go over many of the scenarios in which scripting is supported in one fashion or another, and we'll learn what these scripts do, as well as the context in which they execute—whether on the client, or the server.