If it is on the desktop screen you just right click on the icon and select delete. from there if you're on a windows computer it goes to your recycle bin then you right click the recycle bin and a little rectangle pops up an in that rectangle it says clear recycle bin and once you press that all of the stuff that was in there is deleted. now if your on a computer that has chrome os installed you just go to the files screen and right click what you want to delete and click delete and it's gone.
A string is generally considered as a data type and is often implemented as an array data structure of bytes (or words) that stores a sequence of elements, typically characters, using some character encoding. String may also denote more general arrays or other sequence (or list) data types and structures.
Generally I'd recommend not buying one online, tends to be cheaper from a shop - and better used, although their are some risks with 2nd hand devices, I think the big price cut it worth it.
If you did want to buy online, maybe Amazon or Ebay?