-A certifier domain can be specified with the `-n' or `--domain'
-option. A certifier trust level can be specified with the `-t' or
-`--trust' option (default is `full'). A certifier trust depth can be
-specified with the `-d' or `--depth' option (default is 1). `a' may
-be used in place of `add-identity-certifier'.
+Using the `-n' or `--domain' option allows you to indicate that you
+only trust the given KEYID to make identifications within a specific
+domain (e.g. "trust KEYID to certify user identities within the
+@example.org domain"). A certifier trust level can be specified with
+the `-t' or `--trust' option (possible values are `marginal' and
+`full' (default is `full')). A certifier trust depth can be specified
+with the `-d' or `--depth' option (default is 1). `a' may be used in
+place of `add-identity-certifier'.