HDMI extenders are required for all long HDMI cables without an extender or a special chip in the cable, the normal maximum length for a HDMI cable is about 50 feet depending on the gauge of the cable and the power of the signal source.
These are basic extenders, long distance extenders and HDBaseT.
Basic extenders have HDMI female connectors on both sides and have circuitry that rebalances the signals and retransmits them up to another 50 feet. Some of these will require power where others will draw power from the source through the signal.
Long distance extenders will change the signal and transmit it over a different medium or type of cable. Some of these turn the HDMI electrical signal into an optical signal and others send the information over Cat 5e or Cat 6 network cable. This requires dongles on each end and can require either 1 or 2 of the Category cable.
HDBaseT is a technology that takes the dongle a step further and allows for the video to be transmitted over a network just like ethernet or other network signals. It allows for the data to flow through switches and has added Power over HDBaseT or POH for the devices to be powered remotely. It also allows for USB to be transmitted at the same time allowing the HDBaseT Device to become a KVM switch.