What are the problems with highly correlated variables? and what does these problems mean?

Question

Actually I have one dependent variable and four independent variables. but pearson coefficient shows that they are highly correlated. does that mean that all the variables have similar reason of growth.

Answer 1

there is no problem. they have the similar reason of growth.you are correct

Answer 2

if your independent variables are highly correlated with each other there could be multicollinearity in your model.  This won't affect your model's reliability per se, but it will affect the individual predictors.  When two of your independent variables are highly correlated you have a harder time associated a change in the dependent variable to one or the other correlated independent variables.  This can lead to large standard errors for the individual predictors.