Capitalised words
In English, capitalization is the use of a capital letter at the beginning of a word. This is done for proper nouns, which are the names of specific people, places, or things. Common nouns, on the other hand, are not capitalized unless they are the first word in a sentence.
There are other rules for capitalization as well, such as when to use a capital letter for titles and for abbreviations. But in general, if you’re unsure whether or not to capitalize a word, you can err on the side of caution and leave it lowercase.