What a word counter measures
The core metric is the word count: the number of whitespace-separated tokens in your text. "Word-counter" counts as one word; "word counter" counts as two. Hyphenated terms are usually treated as a single word, and punctuation attached to a token does not create an extra word.
Alongside words, the counter reports characters with and without spaces, the number of sentences (split on terminal punctuation like ., !, and ?), and the number of paragraphs (blocks separated by blank lines). Together these give you a full picture of your text’s size and shape.