As you are working with jQuery you have to include jQuery library in your code files in order to utilize jquery features. Its easy for you to decide whether to include .js or .min.js extention of jQuery library.
Functionality wise both are same. The only difference is jquery.min.js is the compressed version of jquery.js. If you are working on development machine then you should use jquery.js whereas in production or where you web site is hosted should use jquery.min.js file. It will decrease page load-time for your webpage using jQuery.
Also note jquery.js is neat and more readable with comments for developer’s guide .