Understanding the Meaning of Bliss

On a bright sunny day, the children decided to go to the park. They were filled with bliss as they played games and ran around the open fields. As they enjoyed the fresh air and sunshine, they laughed and chatted amongst themselves, creating memories that would last a lifetime.

In this passage, the word 'bliss' describes how the children feel during their time at the park. What does the word 'bliss' mean in this context?