Opens the file found at path filename, and reads the entire file. Returns the file as an array of bytes. Commonly this array of bytes is uploaded to a database table with a column of type BLOB (Binary Large OBject). This upload would be done through an INSERT or UPDATE SQL statement run through the system.db.runPrepUpdate function. You could also write the bytes to another file using the system.file.writeFile function, or send the bytes as an email attachment using system.net.sendEmail.