It's a custom to offer bread and salt to guests (bat maybe also this custom can be debatable). As I said nowadays it's very old-fashioned and almost extinct. In Czech Republic it's used only occasionally to welcome official visits of foreign politics here or local politics on traditional events. So it maybe count only as relict of old tradition, which is keep only by some events and not by ordinary people (my friends offered me bread and salt once, but it was meant as a joke).