Standard Normal distribution has a higher peak in the center, with more area in this región, hence it has less area in its tails.
Student's t-Distribution has a shape similar to the Standard Normal Distribution, with the difference that the shape depends on the degree of freedom. When the degree of freedom is smaller the distribution becomes flatter, so it has more area in its tails.
Student's t-Distributionwith 1515 degrees of freedom has mores area in the tails than the Student's t-Distribution with 2020 degrees of freedom and the latter has more area than Standard Normal Distribution
