What do you understand by standard deviation?

Hint: Karl Pearson developed the principle of standard deviation in 1893. It is the most commonly used and important measure of dispersion. Its importance stems from the fact that it is clear of the flaws that plagued previous approaches and meets the majority of the properties of a good measure of dispersion.

Complete step-by-step answer:
The standard deviation is a measure of how far a collection of data deviates from its mean. It calculates a distribution's absolute variability; the higher the dispersion or variability, the higher the standard
In statistics, the standard deviation is simply a measure of dispersion. It depicts how the individual data points in a data set deviate from the mean. The square root of the mean of the squares of the deviations of all the values of a sequence taken from the arithmetic mean is the standard deviation. The root mean square variance is another name for it.
Sigma is the symbol for standard deviation. We come across standard deviation very often when dealing with statistical problems. The standard deviation is an indicator of statistical data dispersion. The ability of data to scatter through a region is known as dispersion or variation. The divergence of the data from its average or mean location is measured by dispersion.

Note: Always keep in mind that the Standard Deviation can be calculated in one of two ways for individual observations:
Calculate the items' variance from the actual mean.
Calculate the item's variance from the assumed mean.