Comic book captions have various functions.

Captions may show the passage of time with words like Later... Afterwords... Meanwhile... One Year Later..., and co on.

A caption can also used to change settings. These captions use phrases such as Back in the Newsroom, On Mars, At Ben's House.

Sometimes a caption combines a time and setting change: Later in the Cafeteria, That night in the Castle.

Finally, captions are used to set a mood, create atmosphere, or provide information you can't get from dialogue

Comic book captions are often boxed in, as this example from Mr. Fixitt shows. Captions provide information that would be awkward to convey with dialogue

Dialogue in comics usually appears in balloons. As a general rule of thumb, most panels have no more than three balloons. The norm is one or two dialogue balloons per panel. For years in the comic industry, the rule was to never use more than 20 or 25 words in a balloon. A total of 50 words in a panel wss considered a lot. The rules are changing. Some modern comics fill a balloon with 40 or more words.

The fewer panels you use on a page, the more room you have for art and dialogue. In truth, though it is best to avoid long-winded speeches. Avoid using dialogue for something that can be pictured in art.

A quick reminder: what a character thinks or feels can also be shown using thought or whisper balloons.

In this example from Archie comics, see Archie's thoughts are in a thought balloon. Alice Adam's dialogue appears in a speech balloon.