To use the advanced search feature, the pull-down menu will offer options such as "contain" or "is".  "Contains" means that the field has particular letters.  For example,  NC and CA are both US states containing the letter "C".  Searching this way you will get members from North Carolina, South Carolina, British Columbia, Connecticut, Colorado, California and other locations.   If you want a specific state such as North Carolina, use the search term "Is".  That means the search can only return a member from North Carolina.  Also searching by "NC" or "North Carolina" will return different results, depending on how the member set up their profile.