Question: What does the horizontal bar indicate and how to use it in my measurement?

![photo of DMM display](https://i.stack.imgur.com/B9YFy.jpg)

Answer: 
That bar at the bottom of the screen simulates an analog meter - the length of the bar increases with increasing digital readings. It is often easier to observe a varying voltage by looking at the bar than trying to interpret rapidly changing digits.
Digital multimeters have measurement ranges like 0-200 mV, 0-2V, 0-20V, 0-400V etc. 

Bar graph shows how near you are to the end of one range.