Which case to use
Sentence case capitalises only the first word of each sentence and is the easiest to read for most text. Title Case capitalises the main words and leaves small words like 'of', 'and' and 'the' in lower case, the style used for book and article titles. UPPER CASE is best kept for short labels, because long passages in capitals are hard to read.
Capitalized Case capitalises every word, which some brands use for buttons. Fixed text typed with Caps Lock on? Choose Sentence case.
For developers
camelCase, snake_case and kebab-case turn phrases into names for variables, database columns, files and URLs. Punctuation is removed and words are joined with the right separator.