The activities you have listed below are not generally a full time job/occupation and thus the names given to them are vary depending on the company/context of the situation. My best guess/suggestion for names of the activity/person conducting such are as follows: The one who behind a stand on the supermarket promotes a product and offers free samples: Sales Promoter The one who assist guests who come for a conference or seminar: Host/Hostess but probably closer to Guest Relations Associates, or Conference Concierge or something along those lines. The one at exhibitions who you can ask about the exhibition itself - the very act of participating in exhibition makes them "exhibitors" but companies would call them differently like Sales Consultants, Marketing Experts, all fancy names. But one name you should not call them is "Exhibitionists" ! (joke) As for your title, hostess.stewardess, the "politically correct" way of address them in flight context is "flight attendants"

Stewardess- flight attendants or cabin crew on a plane

Could you give me the right names for these types of hostess or stewardess hostess -The one who behind a stand on the supermarket promotes a product and offers free samples hostess- The one who assist guests who come for a conference or seminar hostess-The one at exhibitions who you can ask about the exhibition itself. A stewardess- one who serves you on the plane