Before primary school, there was basically no affection between men and women (even childhood friends knew nothing at this time). From elementary school to junior high school, the concept of love is naive, and you may be curious about the opposite sex, but you don't know if it is love at all. Most people's love at this age is like imitating a youth idol drama or a youth romance novel, and many things are superficial. The most common expression is: I like you, so I will buy you snacks. Although this view of love is somewhat naive, it is the simplest, and liking is simply liking. I won't consider family and other factors. And this kind of love is very simple, probably because the other person looks better, so it is particularly difficult to maintain, and the final result is almost failure.
Although it still belongs to the category of puppy love after high school, everyone has learned to think and the concept of love is relatively mature. At this age, everyone has learned to express love in their own way, and no longer foolishly think that love now is forever. They have learned to consider realistic factors, and many couples have begun to plan for the future. Although the hope is still slim, some couples can encourage and help each other and finally get into the same good university.
Love after college, as the concept of love becomes more and more adult, the behavior becomes more and more mature, and marriage after college is not without it. Although their understanding of reality is still lacking at this age, they have learned to consider realistic factors, family environment and so on. But also know what to do to maintain this relationship and make clear plans for the future (of course, some people still love it like high school students).
I haven't experienced the concept of love since I entered the society or after work, so I won't say it.