JOSSO, or Java Open Single Sign-On, is a computer program that helps you log in to different websites and applications without having to enter your information over and over again.
Imagine you are at a big playground with lots of different play areas. Each play area has its own person who checks your ID card to make sure you are allowed to play there. Every time you want to switch play areas, you have to find the person who checks your ID card and show them again.
But with JOSSO, you only have to show your ID card once, and then you can go to any play area without showing it again! It's like having a magic sticker on your clothing that lets all the play area workers know you're allowed to be there.
JOSSO works the same way, but instead of a magic sticker, it uses something called a "token" to show that you are allowed to access a website or application. Once you log in to JOSSO, you can access any website or application that uses JOSSO without having to enter your information over and over again.
So, just like at the playground, JOSSO makes it easier and faster for you to move between different websites and applications without having to constantly re-enter your information.