Newbie: Objective Function

Question

I am reading the book "Data Science for Business" by Foster Provost & Tom Fawcett. Only a fourth of the way through.

I am unclear about the concept of Objective Function. I will nevertheless take a stab and would like to seek feedback.

Say that we decided to use standard linear regression for a given problem (assume we have training data). Is the goal of objective function to determine the best parameters (weights) for this training data?

Thanks in advance!