This brief published by the Education Commission of the States reviews the spectrum of assessments required or authorized under the Every Student Succeeds Act (ESSA). The author describes the usefulness of a well-designed assessment program for education stakeholders. For example, school districts and states may find assessments useful in (a) evaluating school performance, (b) designing appropriate interventions for low-performing schools, and (c) comparing performance of different subgroups of students. The brief includes hyperlinks to learn more about a broad range of assessment styles including formative, summative, competency-based, and computer-adaptive assessments. The author also provides a hyperlink to ESSA assessments in all 50 states. A glossary of terms furnishes basic information about choosing and using assessments.