Errr...
If you think of a hard drive being like a shelf which you put books on, and each book represents a partition holding data in it, and the books can be varying widths (partition size) to fill up the whole shelf space.
Formatting a partition is like ripping out the contents pages of a book on the shelf so that you dont know whats in the book ( partition ) anymore. This effectively makes all the pages in the book available to be re-written over and so it can be considered free space. The book(partition) still remains at the same overall size and place on the shelf.
Deleting a partition is like taking the book off the shelf so that there is complete blank space to place a new one back in.
Deleting all the partitions is like taking all the books off, creating a complete empty space into which you can put new books/partitions of new sizes in.
Lastly, there is little point formatting a partition before deleting it. The partition delete will delete all the data in the partition.*
* Well, kinda ... in simplistic terms, deleting data in very very general terms is often a case of just marking the start of a file and the space it occupies as being available to be written to. It doesn't actively go through the whole file space and make all the data zeros or anything like that. As a result, as long as the space hasn't been written over, it is possible to scan the free space and still read the original data that the deleted file had and re-create it.
Going back to books... if a file was a sentence on a page. Deleting the file would be like rubbing out the capital letter at the start ... the rest of the sentence still remains avilable to be read if you really really wanted to. .... but thats a whoel different topic !
