This is because the generation and interpretation of the various chemicals substances signaling our feeling and understanding of love takes place in the brain. I will be analytically illuminating the different kinds of love as defined by the oxford dictionary.
The oxford dictionary defines four different kinds of love which expressed by humans i.e. agape, philia, storge/affection and Eros. Affection is used in reference to the strong feeling of affection towards someone or something. This kind of love is usually expressed among members of the same family; it is the love felt and shown by parents towards their own children, the feelings of love expressed among children and towards their parents. This is also the kind of love felt between friends and sometimes it culminates into romantic relationships in which the couples become best friends. This type of love is usually unconditional, sacrificial and drives people at forgiveness hence assuring them of comfort and safety.
Eros or romantic love on the other hand is defined as referring to the strong feeling of affection towards someone you are sexually attracted to. it is characterized by intense feelings of passion which arouse romance and makes one use the phrase “I love You.” in other words it is the love that culminates in sex and love making between the partners and unless moved to a higher notch it may fade with time since it centers mostly on the self. In case the person expressing the love for some reason stops feeling good about the relationship then they may stop showing their emotions to the partners. This is the kind of love that culminates into marriage between the two people if the emotions are taken beyond sexual satisfaction to seek companionship.
Agape refers to a kind of unconditional love which looks past the surface and accommodates the other person as they are regardless of their shortcomings and flaws. It is what we all strive to have and show