"Infatuation" comes from the Latin root fatuus (fatuous in English), which simply means "foolish". Literally meaning to be, or to be made a fool for something. This can refer to anything, religion, a person of the same sex, an idea, or even a hobby, but then of course the word has come to take on romantic connotations.
The infatuation you're talking about, romantic infatuation or infatuation with a person of the opposite sex is usually characterised by very intense, but temporary feelings mainly founded on imagination.
For whatever reason that person comes to represent some ideal, or something we imagine as perfect in our minds, this is possible only because we don't know about or don't consider the "reality" of that person, their flaws, weaknesses, et cetera.
Also (in my experience) this feeling is supported and made even stronger when we cannot possess the person after whom we pine. When something is just out of reach, it seems that much more valuable and perfect, "above us" in some way, the perfection, the hapiness in our lives that we aspire to but can never quite reach.
And unfortunately, feelings of love or adoration release endorphins in the brain which account for feelings of euphoria, giddiness or happiness we feel whenever we think about this thing.
Infatuation is an illusion based on a lie that we tell ourselves: "This thing is perfect, this thing will make my life perfect, if I had this thing, I would never want or need anything else."
Of course, if we are able to step back and look at the situation objecively we find that this is of course false, and that this thing, like everything else in life is flawed and normal.
So that's infatuation, I won't even pretend to attempt to define "love". Tried it, three times, I came to the conclusion that love as a word is simply sex coupled with feelings of familiarity and adoration that come about between people in a relationship, and that love as a concept is the highest spiritual aspect of human psychology and existence which gives meaning to our lives and is the basic bond that holds together society and the human world as we know it so...good luck with that.