An unstandardized coefficient represents the amount of change in a dependent variable Y due to a change of 1 unit of independent variable X.
Use of Unstandardized Coefficients in Regression
Unstandardized coefficients are usually intuitive to interpret and understand. Since they represent the relation between raw data, they can be used directly in calculations and analysis. They can also be used to make comparisons within the regression equation when just one measurement scale is in use. If several measurement scales are in use, standardized coefficients are preferred for comparison (see below).
Weak Point of an Unstandardized Coefficient
Unstandardized coefficients are less useful for direct comparison when the measurement scales of the independent variables are different. In these cases a larger number may still point to a smaller effect, and to pinpoint the effect size of variables, you may want to standardize your coefficients first.
For instance, in an analysis where you regress IQ scores on both years in college and income level, your variables will be on completely different scales and so each unstandardized coefficient (one in IQ/$ and one in IQ/years) can’t be compared with another unstandardized coefficient. To find out which is the most interesting effect one would want to standardize the coefficients first, which means they would both be in terms of standard deviations and so easily compared with each other.
References
Levine, D. (2014). Even You Can Learn Statistics and Analytics: An Easy to Understand Guide to Statistics and Analytics 3rd Edition. Pearson FT Press
Janda, Kenneth. Linear Regression. Lecture Notes from Elementary Statistics for Political Research, 310. Retrieved from http://janda.org/c10/Lectures/topic04/L25-Modeling.htm on July 19, 2018
Wuensch, Tindall, David. Some Notes on Statistical Interpretation. Sociology 502 Lecture Notes. Retrieved from http://faculty.arts.ubc.ca/tindall/soci502/overheads+slides/Statistics_I/Notes_on_Interpretation.pdf on July 19, 2018.Karl. Regression Coefficients: Unstandardized versus Standardized. Retrieved from http://core.ecu.edu/psyc/wuenschk/MV/multReg/Standardized_Regression_Coefficients.docx on July 19, 2018.