The characters you are reading on your screen now each have a numerical value. In the ASCII format, for example, the letter 'A' is 65, 'B' is 66, and so on. If you look at a table of characters available in ASCII you will see that it isn't much use for someone who wishes to write something in Mandarin, Arabic, or Japanese. For characters / words from those languages to be displayed we needed another system of encoding them to and from numbers stored in computer memory.
UTF-8 is just one of the encoding methods that were invented to implement this requirement. It lets you write text in all kinds of languages, so French accents will appear perfectly fine, as will text like this
???? ????? (Bzia zbasa), ???????, Ç'kemi, ???, and even right-to-left writing such as this ?????? ?????
If you copy and paste the above text into notepad and then try to save the file as ANSI (another format) you will receive a warning that saving in this format will lose some of the formatting. Accept it, then re-load the text file and you'll see something like this
???? ????? (Bzia zbasa), ???????, Ç'kemi, ???, and even right-to-left writing such as this ?????? ?????