We use capital letters at the start of every sentence, but there are some words that always need capital letters.
Capital letters are needed for the all names of people, places and dates. These are sometimes called proper nouns.
Book and film titles are also given capital letters. Usually all the words in the title start with a capital letter except little words like 'and' and 'the'. The first word of the title always has a capital even if it is a little word.
Snow White and the Seven Dwarfs
One Hundred and One Dalmatians
Sometimes we write a whole word in capital letters to make it stand out more.
'FIRE!' shouted Jimmy.