Type celtic and mythology in the keyword search box.
Click on Go or hit Enter.
How many items did you find?
To expand your search, think of other keywords to use for celtic and mythology. Parentheses can then be used to group together related keywords and truncation can be used to find other word variations.
Type celt* or irish or ireland and myth* or religion or folklore in the search box and click on Go.
Now how many items did you find?
Nesting allows you to combine all of your keywords in one search and expand and contract your search.