Canned responses are pre-written templates for common questions and other repetitive messages. They save you a huge amount of time when you're dealing with repetitive SMS messages and emails.
Step 1: On an open Contact Card, click the composition box and select the email or SMS icon.
Step 2: Click the canned-response icon alongside the send button.
Step 3: Pick the response you'd like to send from the list that pops up. The response will be inserted into your email or SMS body and (if applicable) subject line.