Canned responses is a Lab feature - you need to Enable it by going into your Gmail Settings under the Lab section.
Canned responses are exactly what the name says - chunks of text you've pre-written that you can quickly insert into an email. It's really useful if you write the same sentences (or paragraphs) to multiple people at different times. You could also use it to set up multiple signatures that you can switch between (make sure you turn off the default "Signature" in your Gmail Settings if you do this).
To create a canned response:
- Start composing an email.
- To save what you've written as a canned response, click on the "More options" drop-down button in the lower-left corner of the Compose window; an additional menu will appear.
- Hover over "Canned responses". An additional menu will appear.
- Under "Save", click on "New canned response" (or, to overwrite an old response, click on the name of the old response).
- A pop-up window will appear. Give your response a name you will recognize ("Informal signature", "Formal signature", "Grading in Writing Lab" - whatever works for you).
- That's it! Your canned response is saved.
Note: This will save ALL of the typing in the email you've written as a single canned response. You might want to set up your canned responses independently of actually writing an email.
Note 2: Canned responses can include images that have been inserted into the email.
To insert a canned response:
- Start composing an email.
- When you get to the point where you want to insert the canned text, click on the "More options" drop-down button in the lower-left corner of the Compose window; an additional menu will appear.
- Hover over "Canned responses". An additional menu will appear.
- Under "Insert", click on the name of the response you want to insert.
- Once it's inserted, you can edit it (if it doesn't quite grammatically fit with the rest of the email).