What is a file - in computers?

File is sequence of bits ( 0's & 1's) . While a software loads the file, it may interpret this sequence in a different manner. Initial bits of a file tells about the file, some useful information. Then follow the data bits of file. While opening a file with notepad, it may directly convert every 8 bits or so, to directly the characters according to ASCII format. Which may be readable or not depends upon the type of file, in what manner this sequence is arranged.