Hi Kristian, You're definitely on the right track but just to clarify a few things: I'm trying to wrap my head around this $_GET function $_GET is not a function, it's an associative array. 1) If you add a question mark at the end of a URL e.g. "?category=books" - the word after the question mark - "category", becomes a variable and the word "books", becomes its value Yes. 2) The function takes a string variable name - $_GET["category"] Looping back to the first statement, $_GET is an associative array, not a function. An array holds a collection of variables, where as a function is for executing a block of code. 3) The function isset(), checks for a variable "category" in the URL Yes, mostly. isset(...) takes any variable you pass to it, and determines if it's value is NULL or not. For example: ``` /* given the url http://www.mywebsite.com/mypage.php?category=books */ isset($GET["category"]); // returns true, because category is a parameter that gets passed to the $GET array isset($GET["foobar"]); // returns false, because foobar is not a parameter, so it does not exist in the $GET array isset($myVar); // returns false because $myVar is not defined. ``` 4) If the variable exists in the URL, the $_GET function takes the value from the variable - in this case, "books" Yep, but to clarify the terminology: "If the parameter exists in the URL, the $_GET array takes the value from the parameter" 5) You can then use a conditional statement to see what the value of "category" is, and run a code block Precisely! Here are some documentation links on the relevant topics: - arrays (http://php.net/manual/en/language.types.array.php) - functions (http://php.net/manual/en/functions.user-defined.php) - superglobals (http://php.net/manual/en/language.variables.superglobals.php) - isset (http://php.net/manual/en/function.isset.php) Hope that's helpful. Answer from Miguel Canas on teamtreehouse.com