Dedication and motivation can often seem like the same things - both are intangible forces that can help propel you towards towards your goals, but there are a few major differences.
Motivation can come from a variety of different sources but to over simplify: motivation can be internal or external. Meanwhile, dedication has to come from within you. No other person or thing can give you dedication, though motivation can lead to dedication.
The other, and perhaps more important, difference between the two is that motivation is fleeting. Motivation will come and go on any given day, often dependent on other factors. Dedication, on the other hand, will always be there once you have it.
Don't get me wrong, both dedication and motivation are vital when it comes to reaching your goals. Whether your goals are related to work, money, family, fitness, or anything else - motivation will get you started, but dedication will allow you to finish the job.
Motivation will make you want to do the work to achieve your goals.
Dedication will make you feel the need to put in the work.