When enabling case sensitive matching we are telling the computer that we DO CARE and that it DOES matter if the text stored in our database is in UPPER or LOWER case. Truth of the matter is, we usually don't care and would normally leave this option unchecked.
When Case Sensitive Matching is Enabled (checked)
Smith and SMITH are not the same.
When Case Sensitive Matching is Not Enabled (unchecked)
Smith and SMITH are considered to be the same.