[newbie scripter]

IMO stock is like a short form, i mean u can supress a code into a line or make a safe function and preventing hack.
for Example

pawn Код:

stock SendClientMessageToAllEx(exception, color, const message[])
{
  for(new i; i<MAX_PLAYERS; i++)
  {
    if(IsPlayerConnected(i))
    {
      if(i != exception)
      {
        SendClientMessage(i, color, message);
      }
    }
  }
}

u can use the above code to send a message to players other than the one u mentioned. Instead of typing

pawn Код:

for(new i; i<MAX_PLAYERS; i++)
  {
    if(IsPlayerConnected(i))
    {
      if(i !=playerid)
      {
        SendClientMessage(i, -1, "~");
      }
    }
  }

u can type

SendClientMessageToAllEx(playerid, -1, "~");