What is meant by saying this statistical test is valid at 5% significance level? what is oversized test? what is liberal test? [migrated]

I have a bunch of tests. The sizes of these tests were inspected under different sample sizes. For every sample size 10000 data sets are generated and then the empirical rejection rate is calculated. The author says when commenting the graphs this test is valid at 5%, the other test is oversized and that other becomes liberal