Isolation and quarantine are key strategies to reduce the spread of COVID-19. If you test positive for COVID-19, have symptoms, or are identified as a close contact of someone who has COVID-19, public health will ask you to isolate or quarantine as appropriate.
This page from the Washington State Department of Health (DOH) outlines the difference between isolation and quarantine and explains why both are important.
DOH also launched an online COVID-19 Isolation and Quarantine Calculator to help you figure out how long you should isolate/quarantine if you have tested positive or been exposed to someone who has.