The t-test is a parametric test of difference, meaning that it makes the same assumptions about your data as other parametric tests. The t test assumes your data is independent, is normally distributed and have a similar amount of variance within each group being compared. A t-test helps determine whether the difference in mean between two groups is due to real effect or if it has occurred randomly.
The Monte Carlo permutation test is a technique used to determine whether the observed difference between two groupsis real or if it has occurred by chance. It is very helpful while dealing with complex data.