The Big Bang is the name of the creation of the Universe itself.
Some people use the term for the very point in time that space was created, while others (including me) use it for the creation and the subsequent quarter of an hour,
because a lot happened here, such as the creation of light and particles, and the "inflation" which was a split second where the Universe expanded extremely rapidly.
Until I get a proper article written, you can read my popular science article about the first 15 minutes,
"The Big Bang — an eyewitness account".