Main reason for using logarithmic scales in graphs and charts is to respond to skewness towards larger values. It may also be used when one axis does not follow a linear progression. It is mostly used when the range of the data on one axis is extremely large. Semi-log graph paper is graph paper which has one linear axis and one log axis. the smallest numbers are 10, 20 etc and the largest numbers are in the range of 1,000,000 etc.
Logarithmic or simple Log papers has both log axis and are used to trace data sets with wide range of values or where the difference between the smallest and largest value is much bigger and is not easy to fit on linear scale.
