Normally, capital and lower case letters are treated as if they were the same. A simple search on the word fish calls up records containing Fish, FISH, fish, etc. Search on a name such as O'Day results in hits with variations such as o'day, O'DAY, and O'Day.
In the advanced search, if you select Match Case, the effect is to reduce the number of hits to find only those with the pattern of capital and lower case letters that you have used.
Why another search engine? Here is why.
by Marpex, Inc.