-screen: a physical screen, describing what is actually on the screen, and a
-virtual screen, describing what the programmer wants to have on the screen.
+screen:
+.bP
+a \fIphysical screen\fP, describing what is actually on the screen, and
+.bP
+a \fIvirtual screen\fP, describing what the programmer wants to have on the screen.
+.PP
+The routine \fBwrefresh\fR works by
+.bP
+first calling \fBwnoutrefresh\fR,
+which copies the named window to the \fIvirtual screen\fP, and
+.bP
+then calling \fBdoupdate\fR, which compares
+the \fIvirtual screen\fP to the \fIphysical screen\fP
+and does the actual update.