Space.com has the article Cosmic Inflation: How It Gave the Universe the Ultimate Kickstart (Infographic).
In 1980 astrophysicist Alan Guth proposed the idea of cosmic inflation, a kind of repulsive gravity that pushes things apart rather than attracting them. Inflation caused an explosive scaling-up of space-time a tiny fraction of a second after the Big Bang. In another fraction of a second, inflation slowed to a more leisurely expansion that continues to this day but is accelerating.
I am hoping this infographic will answer a lot of questions I have about general relativity and inflation/expansion.
There are still a lot of questions, but there are answers I have never dreamed of. Here is one in WikiPedia – Comoving and proper distances.
The integral below is formatted a little strangely, but if you read the description of the variables, you can make sense out of it. The a(t’) belongs under the c, not under the dt’.