What does it even mean to "scan" emails? If Google receives the email, saves it to disk and later retrieves it again, maybe reformats it, is that really fundame

What does it even mean to "scan" emails? If Google receives the email, saves it to disk and later retrieves it again, maybe reformats it, is that really fundamentally different from a technical point of view? It's all bits and bytes after all. Targeted advertising is creepy to humans, because there is some notion that the computer "understands" what you are sending and builds up a profile about you. But, if you take a sober technical point of view, it's hard to accuse Google of anything. Maybe Google should educate it's users more how those ads are generated?