A lot of the same questions here.
1) Radicals are the extreme outliers of any discussion. If they are VERY liberal or VERY conservative to the point of not being within what could be considered the "Norm", the are radicals.
2 Conservative and Liberal are opposites -
Socially, Conservative tends to mean less open, more private, and more aligned to the group, Liberal tends to mean more open, less private, more pushing for change, and more on the outer edges of the group.
Economically, Conservative tends to be spending as little as possible, and only on "needs", Liberal tens to be more free spending, on things that would be "nice" to have.
3 Democrats and Left Wing tend to be the same, and tend to be more socially and economically liberal.
Republicans and Right Wing tend to be the same, and tend to be more socially and economically conservative.