A member variable, aka instance variable, aka field is part of the object that is created on the heap. There is a place inside that object to track the current value of the reference that the variable holds. It stays there until the object itself is no longer referenced by anything, at which time it is rounded up by the gc.
A local variable, aka automatic variable is not part of the object. It is a variable that is created automatically when a method or block of code is executed that declares the variable, and lives on the stack that is associated with the method. When the method is over, the stack for that method is rudely cast aside and thus the local variable is destroyed.
You might enjoy reading
Not all Variables are created Equal.