The students t-test is a method of testing hypotheses in statistics. Specifically, the test is a way to measure the significance of a difference of means between two distributions, such as an observed distribution compared to the Normal distribution. The test relies on assumptions of normal distribution, non-sphericity, kurtosis and heteroskedasticity.
Often the students t-test is used when comparing the mean between two groups, even if the standard deviations of the two groups are unknown.