Special characters are symbols or punctuation marks that are not letters or numbers. They are used to add emphasis, clarity, or formatting to text, and can also be used for various other purposes like coding and mathematical operations. Examples include punctuation marks like !, @, #, $, %, and symbols like &, *, ^, (, ), -, _, =, +, \, |,, {, }, ;, :, /, ?, ., >, etc.