Sean Carroll has compiled a nice list of 19 items of what we currently know and don’t know about the Big Bang, in the hope of dispelling some common misconceptions. I found items #12 and #16 helpful in clarifying my own thinking about how to express these ideas.

12. The early universe had a low entropy. It looks like a thermal gas, but that’s only high-entropy if we ignore gravity. A truly high-entropy Big Bang would have been extremely lumpy, not smooth.

16. Dark energy is not a new force; it’s a new substance. The force causing the universe to accelerate is gravity.