"Mounting a drive"

[rs]

Hallo 
Could  someone  explain  exactly what is meant by "mounting" a disk. I
understand  that it is making a disk available for use, but would like
to understand the implications of the term and what abilities it
confers.

Part  of  the  purpose of the question is that I am trying to find out
how  I  can  have more partitions and detachable drives than there are
letters in the alphabet.

Best Regards,
Richard Shoebridge