Constructors are not part of the AppleScript terminology, but user-defined functions. Basically, they are handlers concibed to create objects from scratch, initializing their values with some data. Making use of other words: templates for applescript items (handlers, properties, etc.).
--> this is a template (the constructor) to createCharacter(x, y, z) script blank property userName : x property userAge : y to sayHisName() say "My name is " & userName & " and I'm " & userAge & " years old" end sayHisName script dog property dogName : z end script end script end createCharacter --> we use the template to create two characters, called "John" and "Harry" set John to createCharacter("John", 13, "Bo Derek") set Harry to createCharacter("Harry", 54, "Tyler Hamilton") --> we use the handler "sayHisName" of the new object called "John" tell John to sayHisName() --> and we are interested in the property "dogName" of Harry's dog say dogName of dog of Harry