Binary files give you the data byte for byte as it is in the file.
Text files don't, exactly. In Windows, for example, a newline is stored as hexadecimal 0A 0D, but when read in "text" mode, you only get a "\n". (Why this is, I don't know... probably dates back to some issue long ago... I think dealing with consoles, but don't quote me. Too young.
)
If you were to try to read a binary file as text, you wouldn't get the data you needed, as it probably wouldn't be text. Text files are things like *.txt, *.html, *.php, anything composed of text characters. Binary files are things not meant to be read by humans: *.zip, *.exe, *.gif, *.bmp, *.mp3 (both lists go on an on)
Here's a
link. Also, try searching
Google.