on Jane Friedman site:
Landing your novel opening can be tricky. On the one hand, you need to get the reader sucked into the present moment of the story as it’s unfolding; on the other hand, there’s a lot you need to explain about the past, which is precisely the sort of thing that puts readers to sleep.
This info is generally known as backstory (essential information about the characters’ past) and exposition (essential information about the context of the story). Getting it right is one of the biggest challenges you’ll face with your novel.