One of the most common tips given to beginning writers is: show, don't tell. Telling is usually the most simply way to get your idea onto paper (or a computer screen), and that is okay for first drafts, but it should be corrected in editing in order to strengthen your story. The problem is, many writers are not sure exactly what is meant by this or why it showing is preferred over telling.
What is wrong with Telling?
Telling pulls the reader out of the story by making them aware of the writer's voice. Readers want to experience the story. In order for them to forget about the words on the page and become fully immersed in the story, they need to experience what is happening. Of course, the opposite of experiencing the story is being told the story. A story is not engaging when it is told. This is where the advice comes from. Another problem with telling is it's often vague. When you tell a reader something, such as: he was scared, it will mean different things to each reader. Show your reader what is happening; don't tell them.
What is showing?
Showing sounds visual, and this is part of the confusion the beginning writers experience when they're told to show instead of tell. What is really meant by show is that you need to let the reader experience what the characters in the story are going through, what they are seeing, and what they are feeling. By allowing the reader to experience the events of the story, instead of telling them the events, you immerse them into the story world. This makes for a more engaging and exciting story.
You can think of the difference between showing and telling as the difference between going to a movie theater and watching the events unfold vs. having a friend recount the events that happened.
Do I always need to show?
There are always exceptions to a rule. In this case, the main time that telling works better than showing is when you're writing about something minor. Showing often uses more words than telling and if you're including a trivial detail in your story, there's no need to dedicate a lot of space to it.
How to show instead of tell.
Now that you know why telling is bad and what showing is, let's go over how to fix it. I'm going to do this primarily by providing examples that tell, and then transforming them into examples that show.
The above is an extreme example of telling. In essence, when you read that example, you will not experience the story, you'll experience me telling you a story. You'll know what happened, but not have experienced it. Also, it is vague and hard to see what's really happening. People read in order to have an experience that they wouldn't normally have in real life. Here is an example of showing:
You can see in the second example that it is more specific and that it provides the reader with an experience. Instead of the reader being told that bob was attacked, you show them that a man jumped out from a bush and flailed a knife at him. Also, instead of being told that Bob is scared, the reader sees Bob sweating.
I'm going to go more in depth on emotions as that seems to be where many writers have difficulty showing instead of telling.
The above is an example of telling. You can clearly see how the reader would get little from the above statement. Being sad can mean a variety of things to different people, and it also is hard to picture. Here is an example of showing:
These are simplistic examples, but they should get they point across. In one, the reader will just know he's sad, but that's it, and depending on the reader they will think different things about being sad. When they read the second sentence they will see tears rolling down his face. They'll know he's sad, but they also know more about it.
It is often unnecessary to tell because it will be implied by the context and by the scene that you paint in the reader's mind. This also falls under the premise of understanding that your readers are smart and they can figure things out for themselves.
Showing internal emotions.
For emotions that the character is experiencing, but not showing to the outside world, there are many ways to avoid telling. One thing you can do, is to say, John bit his lip, refusing to let his anger boil over. You're still saying he's angry, but because you provide a specific example, it flows and won't pull the reader out of the experience. You can also let the reader infer what emotion it is by saying, Fred's stomach turned, twisting into a thick knot. This is much better than saying Fred was nervous.
I hope all of these examples have helped you know the difference between showing and telling, why telling is bad, and how to transform a weak sentence that tells into a strong sentence that shows. If you are still confused, please leave a comment and I'll do my best to explain more.