I have come across this term "streamlined" user interface, and I wonder how is it different from other user interface type? What is the different between "streamlined" and "non-streamlined" user interface?
Conceptually, a streamlined UI is one where every UI element is exactly where the user wants it at the exact moment that the user needs it, and is not visible when the user doesn't need it.
Obviously, what constitutes "streamlined" is semi-subjective. There are some objective measurements, and there are a lot of objectively wrong things you can do with UI design. People generally design a streamlined UI either though solid UX experience and design principles, or by sitting someone down and letting them play it, then seeing where they have trouble.
Not having the source from which you read the terminology, I'm going to guess it was simply referring to the literal definition of the word "streamlined."
stream·lined [streem-lahynd] adjective
- having a contour designed to offer the least possible resistance to a current of air, water, etc.; optimally shaped for motion or conductivity.
- designed or organized to give maximum efficiency; compact.
- modernized; up-to-date.
That is, a streamlined interface would be one that is efficient, not clunky, intuitive, and gets the user exactly what they need without overwhelming them. It's often used as a "buzzword" with others like "web 2.0", "blogosphere", and "rich". These words are sometimes thrown into conversation online in an attempt to sound trendy.