IP Phones or Internet Phones are regular telephones, that work using Ethernet or wifi and supports Internet Protocol’s such as SIP, IAX2, H323 rather then using 2 wire PSTN interface.
IP Phone Adapters are FXS creators that generate a PSTN 2 wire dial tone via an Ethernet or wifi phones.
The latest IP Phones now include Cordless and 5 band regular Cellular phones that have wifi or support 3g or hpsda service that allows them to offer IP telephony like the Imate , HP Ipaq or the new Nokia e series phones.