Its meant to show emphasis and make something important so that it catches your eye. You are going to be drawn to things in CAPITAL LETTERS like that you cant tell me you didnt look at that and that it didnt stand out. So it matters to the importance.

It is so that the word is emphasized. Like you NEVER put anything in your ear smaller than your elbow. NEVER is emphasized so that you know NEVER means NEVER!! period!!

they just have a need to stand out or try to. Usually names,states,God etc. are the only words needing capitals.

1-17-2017 English has rigid rules requiring capitalizing certain letters and punctuation marks at certain places. Biblical Greek did not, so there are interpretation errors because of that difference. A capit is a head. Capital is the adjective form, and originally meant the head stone on a decorative column. People sometimes wrote slogans on capitals, which meant they wrote with a chisel, so an alphabet was developed using mostly straight lines and all letters the same height. Another alphabet called cursive was used for handwritten messages. It used mostly curved lines and loops from letter to letter, with some letters going above or below the line of writing to give a pleasant appearance. A few hundred years ago some story tellers developed a new style of story telling: the happy ending. The style was called novella historia, "new story". Because they wrote in languages based on Latin, the name of the style was changed to "romance" while the book was still called a novel. Those writers used a mixture of capital and cursive letters in a rigid pattern to make it easier to read their works, and their style became the rules of writing for all modern languages.

I capitalise a word in a sentence to EMPHASISE it.

You mean 'CAPITALIZE'? If you are talking about writing only the first letter of a word with a capital letter, this usually comes from the rules of capitalization in English. See there for some explanations: http://grammar.yourdictionary.com/capitalization/10-rules-of-capitalization.html - If you are talking about writing a specific word or a part of text in ALL CAPS, 'This style can be used in headings and special situations, such as for typographical emphasis in text made on a typewriter. With the advent of the Internet, all-caps is more often used for emphasis; however, it is considered poor netiquette by some to type in all capitals, and said to be tantamount to shouting.' Source: https://en.wikipedia.org/wiki/Letter_case#Usage