"24" might be a default channel number for certain camera brands (like Axis or generic OEM devices). "2021" acts as a filter to find active servers from a recent timeframe, filtering out the "dead" links that dominate these types of searches.
The query is a "Google Dork" commonly used by security researchers and enthusiasts to identify publicly accessible IP security cameras , specifically those manufactured by Axis Communications. inurl view index shtml 24 2021
This is the default file path and filename for the web-based viewing portal of many older network camera models (often those manufactured by Axis Communications or similar OEMs) [2]. "24" might be a default channel number for