SWR, or standing wave ratio, always comes up when discussing antennas and feedlines. Although it’s by no means the most important element of antenna performance, it’s the easiest to measure, and thus probably the parameter most talked about. This video explores SWR in some detail.
If you want to play with the spreadsheets, you can download them by clicking here. This downloads a zip file. Note that the spreadsheets are in Libre Office format. The spreadsheets were primarily designed simply to create graphics for the video. Note that they’re probably only accurate for mild excursions from the default values.