What do carrier bars represent?

[ardchoille50]

I mainly use an iPhone 6s and an iPad Pro 9.7 as my daily drivers. I notice that, on my iPad Pro, I usually see 2 out of 5 bars (see attached pic) while my iPhone 6s usually has 4 out of 5 bars. However, opening various web pages doesn't seem to show any difference in speed or quality between these two devices.

Given that I know next to nothing about how the carriers work, I'd like to learn more. What do the carrier bars represent? Was I incorrect in assuming that signal strength dictates download speed?

 

[Tech198]

bars indicate signal strength only. won't necessary decrease with usage, but depends on time of day, how many people on cell tower in suburb. For example my iPhone 6 is mostly only 1 bar at all times, yet transfer speeds when doing speed tests are still 25Mbps on 4G. There is no "how many bars equal" thing because it all varies.

 

[ardchoille50]

bars indicate signal strength only. won't necessary decrease with usage, but depends on time of day, how many people on cell tower in suburb. For example my iPhone 6 is mostly only 1 bar at all times, yet transfer speeds when doing speed tests are still 25Mbps on 4G. There is no "how many bars equal" thing because it all varies.

Thank you, this seems to confirm my suspicions.