Inkan - Hanko

In Japan, seals in general are referred to as inkan (印鑑^?) or hanko (判子^?). Inkan is the most comprehensive term; hanko tends to refer to seals used in less important documents.

For personal use, there are at least four kinds of seals. In order from most formal/official to least, they are: 'Jitsu in', 'Ginko in', 'Mitome in', and 'Gagō in'.

A 'jitsu in' (実印^?) is an officially registered seal. A registered seal is needed to conduct business and other important or legally binding events. A jitsu in is used when purchasing a vehicle, marrying, purchasing land, and so on.
A 'ginko in' (銀行印^?) is used specifically for banking; ginko means "bank".
A 'mitome-in' (認印^?) is a moderately formal seal typically used for signing for postal deliveries, signing utility bill payments, signing internal company memos, confirming receipt of internal company mail, and other low-security everyday functions.
'Gagō in' (雅号印^?) are used by graphic artists to both decorate and sign their work.