On the internet there is 2 address types. IPv4 which is the main address type used by the internet, as the internet grows the demand increases and eventually we will exhaust all IPv4 addresses. This is why there is an need for the IPv6.
IPv6 is much greater in terms of numbers for IP addresses. All ISP would assign either an /56 or /64 IPv6 address range. Its possible you maybe assigned singe IPv6 address for a small VPS type service.
If you get an /56 you will have 4,722,366,482,869,645,213,696 addresses. If you get an /64 you will have 18,446,744,073,709,551,616 addresses. If you get an /128 you will have 1 address.
Due to the large volume of IP addresses and being assigned a large IPv6 block, you can choose any IP address within the block you have to use. You can configure the IPv6 address itself against your server and to assign them for your services.