What's the difference between the two methods to jump out of `cin`?

method 1:

string s;
cin>>s;
cout<<s<<endl;

method 2:

while(cin>>w) {
}

I can jump out of cin with enter in method 1, but it cannot be done in method 2. Instead, while(cin>>w && w!="end") can jump out with enter. What makes the difference?