-switches part will only select the first match
-from a multipart/alternative, even if there is more than one
-subpart that matches (one of) the given content type(s).
+switches part will only select the first match from a multipart/alternative,
+even if there is more than one subpart that matches (one of) the given
+content type(s).
+.PP
+Using either
+.B \-part
+or
+.B -type
+switches alone will cause either switch to select the part(s) they match.
+Using them together will select only the part(s) matched by both (sets of)
+switches. In other words, the result is the intersection, and not the union,
+of their separate match results.