If you pick topics from different categories

If you check "HPV" (under "Health topics") and check "Youth" (under "Age"), you'll get:

Only resources that have information about both HPV and Youth.

If you check "HPV" (under "Health topics") and check "Youth" (under "Age"), and check "Faith-based" (under "Setting"), you'll get:

Only resources that have information about all of the topics: HPV and Youth and Faith-based.

If you pick topics from the same and different categories

If you check "Tobacco" (under "Health topics") and "Youth" and "Adults" (both under "Age"), you'll get:

Resources with information about both Tobacco and Youth AND resources with information about both Tobacco and Adults.