From the CCSS website: "The Common Core State Standards provide a consistent, clear understanding of what students are expected to learn, so teachers and parents know what they need to do to help them. The standards are designed to be robust and relevant to the real world, reflecting the knowledge and skills that our young people need for success in college and careers. With American students fully prepared for the future, our communities will be best positioned to compete successfully in the global economy."
Washington State adopted these standards for Math and ELA (English/Language Arts—includes reading) along with 46 other states. Adopting these standards means that students will be taught to the same standards in each state. Now, there will not be a big difference when students move to different states. It also means that states can share ideas and resources for implementing these standards.