diff --git a/certbot/cli.py b/certbot/cli.py
index e8b825a91..bb29a43ec 100644
--- a/certbot/cli.py
+++ b/certbot/cli.py
@@ -873,14 +873,21 @@ def prepare_and_parse_args(plugins, args, detect_defaults=False):  # pylint: dis
         metavar="DOMAIN", action=_DomainsAction, default=[],
         help="Domain names to apply. For multiple domains you can use "
              "multiple -d flags or enter a comma separated list of domains "
-             "as a parameter. (default: Ask)")
+             "as a parameter. The first provided domain will be used in "
+             "some software user interfaces and file paths for the "
+             "certificate and related material unless otherwise "
+             "specified or you already have a certificate for the same "
+             "domains. (default: Ask)")
     helpful.add(
         [None, "run", "certonly", "manage", "delete", "certificates"],
         "--cert-name", dest="certname",
         metavar="CERTNAME", default=None,
-        help="Certificate name to apply. Only one certificate name can be used "
-             "per Certbot run. To see certificate names, run 'certbot certificates'. "
-             "When creating a new certificate, specifies the new certificate's name.")
+        help="Certificate name to apply. This name is used by Certbot for housekeeping "
+             "and in file paths; it doesn't affect the content of the certificate itself. "
+             "To see certificate names, run 'certbot certificates'. "
+             "When creating a new certificate, specifies the new certificate's name. "
+             "(default: the first provided domain or the name of an existing "
+             "certificate on your system for the same domains)")
     helpful.add(
         [None, "testing", "renew", "certonly"],
         "--dry-run", action="store_true", dest="dry_run",