I searched for data about Cepheids light curves (often used as standard candles for measuring distances), and found that all of the data comes in a form of "BVI Photometry" or "BVI Photoelectric Photometry"
For exmaple, the OGLE database gives data as "I band" and "V band" - a quick google search got me to the name BVI Photometry.
Unfortunately, I couldn't find any real explanation of what are does those I-V bands, or how the BVI data is collected and used.
I would love to get some help here: How is BVI data collected, and how does one use it correctly? Even a link to a reliable source would suffice.
Thank you, o kind people of the internet