The acronym HDMI stands for: High-Definition Multimedia Interface.
HDMI ports on a television are used to connect game consoles, Bluray, DVD or hard drive players, stereos, Chromecast, Fire TV Stick, Apple TV, Android TV Box or any other "stick" for video on demand playback.
The HDMI connection includes high definition video and audio in the same cable, from versions 1.0 to 1.3a they only support 2k video, however from version 1.4 support for 4k resolution was included (4096 × 2160 at 24 Hz) in addition to a channel to be able to include or share an internet connection.
The latest version of HDMI to date is 2.1, released in 2017 and including numerous improvements such as a maximum resolution of 10K at 120 Hz.
If you need to have one or more game consoles connected to the TV, a sound system or sound bar, a stick like Chromecast or Fire TV, a DVD player; having 5 HDMI ports you will not have to be connecting and disconnecting cables every time you want to switch between one of these devices, they can all be connected at the same time even if not all are turned on and thus avoid continuously manipulating cables and with 5 HDMI connections you can always have one or two free in case you need to plug in a new device.