IPTV (abbreviation for "Internet Protocol television") is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats.
IPTV is distinguished from Internet television by its on-going standardization process (e.g., European Telecommunications Standards Institute) and preferential deployment scenarios in subscriber-based telecommunications networks with high-speed access channels into end-user premises via set-top boxes or other customer-premises equipment.
For a more broader general overview of what IPTV is and what it is not, please read the article about IPTV on wikipedia.
1 IPTV inside Kodi
To get an IPTV signal into Kodi's PVR frontend your first option is to use an external third-party PVR backend software or stand-alone hardware box that will parse the signal and then in turn repackage and forward it on to a PVR client addon compatible with Kodi, using PVR backend server software such as Tvheadend, VDR, MythTV, and MediaPortal, or a stand-alone hardware box like Njoy N7 or HDHomeRun.
The second option is to use a PVR client addon in Kodi that is capable of receiving IPTV signal directly in Kodi without an third-party PVR backend software or hardware, for which there currently only is one PVR client addon, and that is IPTV Simple Client