What each number counts
Characters
Each letter, digit, space, punctuation mark and line break counts as one. An emoji counts as one even when it is built from several code points, such as a family or a flag, because it shows as a single symbol. Without spaces leaves out spaces, tabs and line breaks.
Words, sentences, paragraphs
Words are split the way your browser splits them for editing, so "don't" and "e-mail" are one word each and Chinese or Japanese text is split into words rather than counted as one block. Sentences end at a full stop, question mark or exclamation mark. Paragraphs are separated by a blank line.
UTF-8 bytes
The size of the text when saved or sent as UTF-8, which matters for database fields, file names and some form limits. English letters take 1 byte, accented letters 2, most Chinese, Japanese and Korean characters 3, and emoji 4 or more.
Reading and speaking time
Based on 238 words per minute for silent reading and 183 for reading aloud, the averages for English non-fiction in Marc Brysbaert's 2019 review of reading-rate studies. Your own pace may be faster or slower.