2 questions

Hey im new so idk alot of things like #KM can some1 explain me please ? sorry bcuz im new im very sorry
2- in US coins i found my coin but its written on numista S P  letters beside each coin what are these letters?

First, KM numbers are a catalogue number (Krause Mischler) given to coins to catalogue them by. Some collectors collect by type or KM number.
Second, D,P,S: Denver, Philadelpia, San Francisco: small mint marks on the coin to say where they were minted.

 As it happens I got the set of coins above from a friend today - it has all three mintmarks - see below.



  The S mintmark is usually on Proof (specially minted) coins, like the middle coin in that set.
Different United States coins have the mintmarks in different places - those above have it below the word Liberty. That set has six coins as there are two different designs on the reverse.
  The KM numbers are the main ones used on Numista - there are others, such you may sometimes on here see Y# for Yeoman, and so on. Here's a recent Topic, and more on Krause Mishler ...

https://en.numista.com/forum/topic9706.html
http://en.wikipedia.org/wiki/Krause_Publications

thx and still waiting for the package