The serums, elixirs and balms are different hair cosmetic products that will seal and nourish the hair that needs it.
These types of products are alloys of different oils and sometimes other ingredients such as humectants (aloe vera, honey, etc.).
The term elixir and serum is used to refer to the same type of product. They are generally mixtures of oils that retain a liquid texture.
The distinction between the two lies more in the marketing investment than in a real difference in ownership. The name "serum" refers more to a medical connotation while the elixir will come closer to the realm of magic.
Balms, for their part, are fatty products that have a thicker texture that is generally solid at room temperature.
The objective of these serums is to propose to the hair a synergy of beneficial ingredients in order to bring to your lengths and/ or your tips an answer to the problems they encounter.
Elixirs can have global or more precise actions depending on the bias of each brand.
Thus some serums or elixir may have been developed to have a specific action on the ends of your hair. Others can be made for damaged lengths or to stimulate hair growth.