This topic has always been one of controversy, but is vital to the understanding of the overall biblical narrative. I have written extensively on it and would highly recommend reading the post below if you are new to this subject in the order given. You may want to start with the video of, in my opinion, two biblical scholars that discuss the Gap.
As you listen and read, keep in mind the following verses:
This then is the message which we have heard of him, and declare unto you, that God is light, and in him is no darkness at all. 1Jo 1:5
And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters. Gen 1:2