Sample 1 is in mauve. Sample 2 is in burgundy. Sample 1 has a much higher variability because the 'typical' value is further from the mean. Therefore the mean is a worse description of sample 1 than of sample 2. Standard deviation Variance is a useful measure of variability but it has awkward units.
Standard deviation is the square root of the variance.
It has the same units as the measure that is varying so is easier to relate to the scores in question. Standard deviation is not some mysterious and arbitrary number that is conjured up out of nowhere. It bears a common-sense relationship to the data and can be easily estimated from histograms. The higher green bar represents the standard deviation of the mauve sample and the lower green bar represents the standard deviation of the burgundy sample. The length of these bars should look like the 'typical' distance from the mean for these two samples.