>It looks like a variable resistor, ...

Agreed. The convention is that when the wiper arrow lies across the resistor that it is a preset potentiometer or"trim-pot" used to adjust or calibrate the equipment. These usually feature a screwdriver adjustment rather than a knob. (The regular potentiometer symbol arrowhead usually just touches the resistor at the midpoint.)

The lower variable resistor seems to set a minimum resistance value for the combination.

[![enter image description here][1]][1]

*Figure 1. A selection of preset potentiometers. Source:[Robot Room](https://www.robotroom.com/Parts/Trimpots-quarter-inch.jpg).*

>... but the rest of the circuit is attached to the tail of the arrow. I feel as though this circuit is trying to describe a voltage divider. Is this true?

That sounds right. It's difficult to know without knowing what the circuit is for and what U and M are.

  [1]: https://i.sstatic.net/XRZGw.jpg

---- 

Update after additional information was supplied:

>U is a voltagemeter and M is a motor. On the device there are two buttons [knobs] that are used to adjust the voltage going through the motor. I figured that this would be done with the two variable resistors. Maybe this will be of some help? http://shop.skolebutik.dk/images/U15040_EN.pdf. 

From the additional information supplied it appears that the incorrect symbol has been used in the diagram. They are regular potentiometers with knobs. I would expect the upper potentiometer's resistance to be 10× that of the lower one as the lower one is the fine adjustment.

It is a little unusual these days to control a motor's speed just with a potentiometer. A variable voltage regulator would maintain the motor's voltage much better than the simple potentiometer arrangement.