Most of your text is easy to put on a web page with no alteration from almost any text file. But what do you do when you need one of those "special characters" that you usually access via your option or alt key when typing in a word processing document such as the copyright symbol (©)? Or you need accent marks as in résumé? Show your <HTML Tags>? You will need to use special code for these special symbols to appear the same on all platforms.
The ISO Latin-1 character set is the standard for the web (and to some extent, UTF-8). Special characters always begin with an ampersand (&) followed by a pound sign and a number (for example #38) or a name (for example amp) and end with a semicolon (;). In this example, & or & will produce an ampersand (&). © or &169; give the copyright symbol (©). Some symbols, such as the trademark symbol (), don't have a name, you have to use their numeric value, in this case: ™.
Web Developer's Virtual Library has a list the characters available online, so does w3schools. And there are many more lists online.
These special characters can give your pages a clean professional look. Have fun!