What is Ordinary Least Squares? What is Maximum Likelihood Estimation? What are the Gauss-Markov assumptions?

What is Ordinary Least Squares? What is Maximum Likelihood Estimation? What are the Gauss-Markov assumptions?
Why are the OLS estimates of regression coefficients equal to the MLE estimates?
What is the standard error of regression? What is the standard error of a regression coefficient?
Why doesnt OLS provide us with an estimate of the standard error?
What is the relationship between MLEs second-order conditions and the standard errors of the
coefficient estimates?
How do the MLE second-order conditions provide us with estimates of:
the standard error of the regression?
the standard error of the regression coefficents?