Rounded bubbles typically surround the words that a character says in a comic. A little tail is connected to the bubble and points to the speaking character. Jagged edged bubbles are used for words that a character is yelling. These usually contain bold lettering to emphasize what is being said in the comic. Dashed lines on the edge of the bubble or faint colored bubbles mean the character is whispering.
Action lettering is often used in comic books and is colored brightly to be easily noticeable. The action words are usually large and printed in a block or bubble letter style. The edges of the words may have a texture to imply movement according to the action in the comic. These words are brightly colored and sometimes have a starburst type bubble around them to bring out the animation of the action or sound effect in the comic's storyline.
Italic lettering is used mostly in captions. Italics are also used for informational narrative boxes that may state the place or time in the comic. Italic lettering is also used in bubbles when a character may be thinking to himself. This lettering style is also used in broken lined bubbles, such as when a character is whispering.
Joined bubbles are used in comics when there isn't much room for a lot of dialogue. Several bubbles may be joined together with connectors if the topic is being changed or the character is voicing a lot of words. Joined bubbles may be used to express sentences being spoken when the character's voice trails off. The second bubble is when they pick up talking again.
Lower case lettering is used mostly for non-verbal sounds or noises produced by characters in the comic. They are usually not real words. Lower case sounds portrayed in comics are usually surrounded by symbols that look like whiskers or asterisks inside the word bubbles.