UX is about defining business goal, and designing solution by using research, planning, prototyping, usability testing ->research, planning, prototyping, usability testing.
UI is about "drawing" interface in a nice way that will enhance experience and improve overall UX, match branding requirements.
Front End dev. is about codding - developing software (client side) that will behave/interact in the way UX designer designed and look like UI designer has drawn.