At some moment in the future, I'll be in the middle of doing something.
We indicate some moment in the future (e.g., "when you come" or "at ten o'clock tomorrow") and we say that at this moment there will be some activity going on. This activity will start earlier in relation to this future moment and it will go on after it. This is the main case when we use the future continuous (future progressive) tense.
Past, present and future continuous
Yesterday at eight o'clock in the morning Dan was having breakfast.
Now it's eight in the morning and Dan is having breakfast.
Tomorrow at eight o'clock in the morning Dan will be having breakfast.
When the boss comes in the office room, everybody will be sitting at the desks and working hard.
At this time tomorrow, I won't be sleeping. I'll be packing my suitcase.
When we arrive at Sarah's place to pick her up, she won't be ready to go. She'll still be choosing which dress to wear.
In the next episode, we'll be exploring the most beautiful places in Cornwall.
Do not forget that there are action verbs and stative verbs. It is wrong to put stative verbs into any continuous tenses. You can use the future simple with the verbs like be, understand, know, love etc.
When I finish this book, I'll know a lot of useful things. WRONG I'll be knowing
After this course, you'll understand oral speech much better. WRONG you'll be understanding