I am sorting out my Gmail account, and started labeling emails, but I can't seem to figure out what the different icons mean in the labeling dropdown menu. There are 3 icons:
- empty
- minus
- checked
You can see them in the screenshot below:
Gmail – What’s the difference between the Gmail label buttons
gmailgmail-labels
Related Solutions
It seems as though there are 3 modes when viewing Gmail messages:
1. Mailbox Mode:
- Invoked by: clicking a mailbox on the top left (e.g. Inbox, Starred, etc.).
- Interface: Blue
- URL: ends with
#inbox,#starred, etc. - Top left button:
- For Spam and Trash: Delete forever
- For all the rest: Archive
- Buttons available: Labels and:
- For Inbox, Spam and Trash: Move to
- For all the rest: Move to Inbox
- Dragging a message will: Move it
2. Label Mode:
- Invoked by: clicking a label on the left.
- Interface: Green
- URL: ends with
#label/[my-label]. - Top left button: Remove label "[my-label]".
- Buttons available: Move to and Labels.
- Dragging a message will: Move it
3. Search Mode:
- Invoked by: pressing the Search Mail button.
- Interface: Green
- URL: ends with
#search/[my-query]. - Top left button: Archive (There will also be the text Search results for:[my-query] to its left).
- Buttons available: Move to Inbox and Labels.
- Dragging a message will: Label it
Note that when you drag a message you can drop it on: Inbox, Starred, Spam, Trash, or one of your labels. If you are in search mode and drag a label onto a Mailbox, it will say Label, but it will actually Move the message.
You will notice that modes 1 and 2 behave almost exactly the same. When you click through to a message from a list, it will show the exact same buttons the list had.
Notice how Move to is only available when the concept of a folder is used. For example, the Inbox acts as a folder since a message can't be both in the Inbox and Spam (or Trash). Similarly, when you press on a label to go into Label Mode, it treats the label as if it were a folder (even though it may be tagged with multiple labels).
When you Move a message it will remove the label/folder you are currently viewing from the message and apply a new one. For example, say a message is marked as label-a, label-b, and label-c. Now you click on label-b on the left to enter Label Mode. Next, you move the message to label-d. What happens is label-b is removed and label-d is added. The other labels remain on the message. The message will now be labeled: label-a, label-c, label-d.
Similarly, if a message is in the Inbox and you Move it to the Trash, it will be removed from the Inbox and moved to the Trash.
When you use the Label feature, you simply choose which labels to add or remove. Nothing will be done automatically for you.
Can you try by changing your text area from plain text to rich text or viceversa, also can you check you gmail account under another webbrowser. If still you are finding the issue you can contact GMAIL directly 
Best Answer
When you have multiple messages/conversations selected and you click the labels button there are three options for the list of labels presented:
If you only have one message/conversation selected then only empty and checked will be used.