Show, don't tell

Show, don't tell is a type of writing technique used by authors. Instead of explaining a story, as in a summary, a writer makes the reader feel what is happening. It creates a picture of something in the reader's mind. When the reader gets a clear mental picture the story becomes more interesting. The technique is used in both fiction and non-fiction writing. 
Examples of show, don't tell.
In the first example, the author is telling what the character feels. In the second example, the author is allowing the reader to picture what the character was experiencing when she opened the door.
Show and tell.
Good writing may involve both showing and telling. A scene shows the reader what is happening. It allows the reader to experience the action and emotions of the people in the story. A summary is often used between scenes to connect them together to create a story. Another use of summaries is in places where a part of the story needs to be brief. Showing takes more words than telling. Less important parts of a story are sometimes mentioned very briefly.