For this question, we highly recommend that you read one of the following in order to get a broad overview of the topic:
Read Chapter 7 ,You Can't Take the Bible Literally, in "The Reason for God" by Timothy Keller
Read Chapters 6&7 in "Questioning the Bible" by Jonathan Morrow
Dr. Jonathan Morrow - assorted topics
J. Warner Wallace – The Top Three Reasons The Bible IS Reliable
Dr. Dan Wallace on The Reliability of the Biblical Text
The context for this video is the number of "variants" in the original text of the New Testament. The New Testament was written in Greek and the various books were copied by hand from the beginning of the church so they could be shared. We do not have any of the original manuscripts. This process of copying has left us with almost 6,000 copies of the New Testament documents in the original Greek. The "variants" are the ways these manuscripts disagree with one another. It is often charged that since the number of variants is very large, the bible cannot be trusted. Dr. Wallace shares the nature of these variants and how they actually help scholars to accurately reproduce the text of the New Testament.