The Surname Index is a searchable database of ancestor names entered by Members. On the Your Profile page (Tab "Surnames"), enter name, location and dates that your ancestor lived. This information will be searchable and fellow researchers may contact you IF an email address is associated with your profile. Note that your contact information is masked and it is your choice as to reply to the query. The data is also available to search engines, so you could be contacted by non-Member.
To limit queries to the relevant, make the proper entries in the dates fields.
The feature is designed for research collaboration, so if that is your goal, take advantage of this tool!