In alphabetical order:
Function: Similar to a procedure, but returns a value or string when finished. You can call a function from inside any parameter by enclosing the function name in "$" characters.
Object: Objects are fundamental to the way Quest works. Objects live in rooms or a player's inventory, and can be moved around, talked to, used on or given to other objects, and more.
Parameter: A parameter is some information that you give to Quest's built-in functions or a function of your own making. Parameters for Quest's built-in functions are usually given between "<" and ">" characters and are separated (if there is more than one parameter) by semicolons. For example, <string; number> is a parameter with two "arguments". Parameters for functions that you make yourself are given in the same way, but between normal brackets () rather than pointy brackets <>, as these functions are themselves part of parameters for something else.
Procedure: A sequence of script commands, which can be called from anywhere within a game.
Room: A place in a game. It could be a room in a building, or it could be a place or part of a place such as a street or shop front - essentially any location you want in a Quest game needs to be set up as a "room".
Script: A command that tells Quest to do something - print a message, move an object, finish the game, play a sound, etc.
String: A word, sentence, or other sequence of letters. These are used in Quest to contain information about user-defined commands, location, etc., and can be used for other things such as objects that can be "written" on by the player, for example.
Tag: A particular property of an object, room etc. that defines how it works and behaves. An object may have a "take" tag, for example, that defines what happens when the object is taken.
Variable: Variables store numbers or text, depending on whether they are numeric variables or string variables. The value of the variable can be read or changed at any time. You can access the contents of a string variable within any parameter by enclosing the variable name with "#" characters, and similiarly a numeric variable can be accessed inside any parameter by enclosing its name with "%" characters.