Algorithms generally means data structures and algorithms. Stuff like hash tables, sorting, linked lists, binary search, trees, tree traversal methods, runtime complexity. Despite what it sounds like, this is considered basic data structures and algorithms, material that can be covered in one CS class. It's material you could learn through self-study over the course of a month.
For front end developers frameworks/stack/communication probably means questions involving basic knowledge of jQuery and how the DOM works. Also might include questions about anything you list on your resume (e.g. if you list Backbone.js on your resume you might expect questions about Backbone's MVC system, events, etc.). Also might ask you non-coding 'architectural' questions where they ask you to describe in broad terms how you would construct something.