The Student's t-distribution is a probability distribution used in statistics, particularly when dealing with small sample sizes. It is similar to the normal distribution but has heavier tails, which allows for more variability. This characteristic makes it useful for estimating population parameters when the sample size is small and the population standard deviation is unknown. The t-distribution is defined by its degrees of freedom, which are determined by the sample size. As the sample size increases, the t-distribution approaches the normal distribution, making it a versatile tool for hypothesis testing and constructing confidence intervals in various statistical analyses.