Caps is an abbreviation for capital letters.
Capital letters (also referred to as uppercase letters) are larger versions of alphabetic characters used in written language. Capitals may serve as the initial letter in proper nouns or titles and/or be used for emphasis within sentences.
The English alphabet contains 26 letters; however, only 24 of these can be considered true capitals – J and Z do not qualify as such letters.
Capital letters serve several different functions in writing. Their most prevalent use is to indicate the beginning of a sentence – they were once printed all in capitals, so this was the only way of signaling new sentences back when all letters were capitals; nowadays, we tend to only use capitals at the start of sentences, although there may be exceptions.
Caps are used frequently to indicate the beginning of a proper noun, which refers to specific people, places, or things, such as continents, countries, cities, or streets.
Since we consider these titles proper nouns, capitals should also be used when writing their titles.
As mentioned above, capitals may also be used for emphasis. This typically happens with words being shouted or presented as important in some way; for instance, you might come across this sentence:
“I DIDN’T DO IT!”
In this sentence, the word “did” is capitalized to demonstrate that its speaker is shouting. This action is known as yelling in all caps.
You might encounter sentences like the following:
“This is the most IMPORTANT thing that you need to know.”
This sentence emphasizes how significant “important” is. All capital letters serve to highlight its significance.
So, those are the main uses for Capitals in written language. You can see they can serve multiple functions; when in doubt, use a capital at the beginning of a sentence or proper noun, as this will ensure maximum impact.