What is a "tester" vs. a regular spray bottle? Thanks.

Testers are the same original fragrances that you find in full size perfume bottles. Fragrance companies manufacture testers to promote their products. Testers may come in a variety sizes and forms of packing - some come with simple white or brown box with or without a cap and may be labeled "Demonstration" or "Tester".   The quality of the perfumes themselves are not affected at all and are the same as the one in retail fancy box.   All testers are sold unused, with the entire original quantity in the container. If you're purchasing for yourself, testers are a great way for you to get perfume for better discount but may not be appropriate for gift.   Hope this will clarify your doubts.