This has been bugging me for a while because the words seem pretty interchangeable when you read them in French. Yesterday, Pascal Dherve made a brilliant video explaining the difference, so I took some notes. You can see the video here
Thank you so much Pascal, your videos are amazing, I learn something every time I watch one. If you're serious about improving your french, I can't recommend this site enough. Pascal also has a facebook page.
Back soon
Amitiès
Jane