Namaste, or its more formal version namaskar, is difficult to translate directly. It roughly means ‘I greet the god in you’ or ‘What is holy in me greets that which is holy in you’. The most beautiful translation we have heard is ‘I honour that in you where the whole universe resides’.
A guest in India is always given hospitality. It is a duty to do so, since the guest is considered a god or godly being.
The namaste is not normally executed in combination with a bow. Indians do not really bow, except when showing deep respect. It is acceptable just to meet the hands in ‘prayer’ before the chest and keep the head upright, while saying ‘namaste’ or not saying anything.
In Europe, it used to be common at meals to set an extra plate for the unexpected guest, especially on Sundays and at Christmas.