Specificity

Briefly I'm going to describe the importance of specificity. But what does it mean?
Basically it means to use specific names when writing. Let's use an example. I'll give you two sentences and you can choose which one sounds and/or feels more authentic to you:

1) The tarantula reacted immediately when I approached, tilting back on its hind legs to bear a grotesquely harry abdomen at me.

2) The spider reacted immediately when I approached, bearing the frontal part of its lower body at me while tilting back on its legs. It was grotesquely harry.

 Not only does the first sentence sound more sophisticated, but it paints a more vivid image of what is going on.

Just to clarify things I'm going to italicize the words which account for specificity in the first sentence:

1) The tarantula reacted immediately when I approached, tilting back on its hind legs to bear a grotesquely harry abdomen at me.

The second sentence lacks these specifics.

"Spider" is a very generalized word. There are thousands of different kinds of spiders in the world, therefore your mind immediately goes to the first spider you can think of; probably one you find most familiar to you. Maybe a brown garage spider or something. Second, "the frontal part of its lower body" is a hell of a lot longer than "abdomen." In a very helpful book called The First five Pages it states that the reader's time is precious, therefore they do not feel like wasting brain power on reading a fifty word description that can just as easily be taken care of with one specific word. Also, describing something like the way I did in sentence 2 clearly signifies an amateur, and makes it seem like you have no idea what the hell you're talking about. It also displays your own laziness in failing to research that particular object.