An external PC monitor has on its rear side a set of ports and connectors, ranging from USB to power supply, and of course, including various types of connectors. With the increasing power of monitors (WQHD, 4K, 8K, 300Hz...), there are different cable standards, each serving different purposes to adapt to these technologies:
VGA: This is the oldest standard and is not commonly used nowadays, as it can only display up to Full HD at 60Hz between your graphics card and your monitor, although this is sufficient for the majority of users.
DVI: Similar to VGA in its functionalities.
DVI Dual-Link: An upgraded cable capable of reaching 144Hz in Full HD and struggling to reach 80Hz in WQHD.
HDMI: We distinguish between HDMI 1.4 and 2.0. The former ranges from Full HD 120Hz to 4K 30Hz, while the latter ranges from Full HD 240Hz to 4K 60Hz.
The very recent HDMI 2.1 is tailor-made for high resolutions, exclusively for 4K and 8K screens with 120Hz and 60Hz respectively.
Display Port: Several versions of this cable have been released with improvements for new screen resolutions.
1.2: Full HD 240Hz to 4K 90Hz
1.3: WQHD 240Hz to 8K 40Hz
1.4: 4K 144Hz to 8K 70Hz
The vast majority of monitors sold in stores today rely on DisplayPort and HDMI ports, as few graphics cards are capable of reaching 4K 60Hz.
You can imagine the requirements for 8K.