eBay

If charge shipping, is that money sent to me or directly to the postal service? For example, if something is $10 + $5 shipping, is $15 sent to me? And what if shipping ends up being less- is the excess money returned, or do I keep it? In other words,...

Are offers on a listing shown to all buyers, or only the seller? And are they meant to be confidential (or am I allowed to let someone in DMs know what my current offers are to see if I can get something higher?) thanks