Fun tech fact:
Those “bars” don’t mean service speed. They represent how close you are to the tower distance wise. Quality of service, speed, network traffic, are all not accounted for.
Alright. My WiFi says it’s at 4 bars but it’s acting like it’s at 1 
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The "distance" is measured by the strength, which generally works as an interpretation until strength fluctuates. Though it could be considered accurate enough to say the bars measure distance, it is easier, and much more clear and concise to say strength.
And I don't mean for this to be flaming or anything like that at all, and I apologize if it is
They don't necessarily represent distance to the tower; I've been at a training for a week and in one of the buildings, the top floor has awful service, and the bottom floor has gold service (I am currently on the bottom floor).
To clarify: I have 1 bar on the top floor, and 4 bars on the lower floor
I think it could vary on OS? Maybe? Or maybe that video I watched was outdated.
It’s actually a measure of signal strength to the tower, measured by the tower itself. The tower tells the phone how many bars to show based on how strong the connection to the phone is.
Yep, and metal etc. in a building or whatever can obstruct signals. I didn't know that the tower measured it though; that's pretty cool.
Wait, what bars? The ones I was thinking about change when I stay in the same location