Although the two roles may sound similar, they serve different purposes.
A Wedding Co-ordinator works for the venue and may be a different person on the day of your wedding compared to the co-ordinator you have been dealing with throughout. They typically get involved in the final weeks of the planning stage and will focus on only aspects/budgets which are related to the venue. It is important to ote that your wedding may not be the only task on your special day therefore they may not necessarily be completely focussed on you! Finally, a Wedding Co-ordinator works from the plans of a Wedding Planner.
A Wedding Planner on the other hand is involved from the very start of the process (or atleast as early as you hire them). You will have the same person throughout all the stages and therefore they will be a familiar face on the day of your wedding. A Wedding Planner has oversight and management of everything related to your wedding, including the overall budget. Your Wedding Themes and Floorplans are designed by a Wedding Planner.