What does "Stay signed in" mean?

When logging in from the website's main page, you can stay signed in from the next time you access the page by clicking "Stay signed in". (This function uses cookies.) By doing this, you can conveniently stay signed in without having to enter your login ID and password each time. You can stay signed in for a maximum of 30 days. Do not check this option if using a shared computer. In order to stay signed in, you must set the browser you are using to enable cookies beforehand. You can cancel the continuously signed in setting by clicking the "Logout" button at the upper right of the main page.