What Is the difference between oysters and mussels? ?

The oyster that you have pictured is  much softer  the scallop is a very firm muscle. 

Now a mussel is a bit firmer than a oyster, a bit softer than the scallop. 

Oysters can be eaten raw, I have yet to see a mussel eaten raw and a scallop can be eaten raw. 

Steamed in their shell with butter, a bit of white wine, some lemon juice the mussels are great with a loaf of crusty baguette to sop up the juices. 

Seared scallops are great as long as they are not over cooked. They are sweet. 

Oysters are good breaded and fried (but what isn't?) They are good in a chowder (or chowdah)  And as a snack lots of people eat them smoked with crackers.

One of the major differences that can be noticed is in the fertilization. In marine Mussels, fertilization happens outside the body. The larval stage drifts for three to six months before settling on a hard surface as a young mussel.

Both are bivalves, but the shell shape and the flesh are both different. Mussels are traditionally steamed in a wine sauce and are delicious. Oysters are served many different ways, but are most delightful raw, on a soda cracker, with a sauce of ketchup, horseradish and lemon juice.

Oysters are oysters and mussels are mussels.  They're different species, like humans and chimpanzees.

They taste different. Also, you eat them by taking them out of the shells and chewing.

Oysters taste really good, mussels not so much.

Eaten on the half shell of course!!!

an oyster is a type of mussel ...................

Oysters pay for public transport, muscles help you move your skeleton. The best way of eating them is with your mouth.