What is the difference between chat and text in texting defualt apps details info?

[Bmw82bds]

So half of his texts being in one convo session even, show some as "chat" and some as "text" in the ddetails info area....and ONLY HIS which is odd to me....he says he doesn't know why either....but I think he might actually....I've always felt his T-MOBILE service and phone somehow has been linked or attached in some way because my logs always say T-mobile stuff ( yes I know metro uses their towers too) but in my google device activity, it shows me going to my HOME area as activity through the day and when looking up the URL and more info, its particular meanings are of Samsung only phones not my LG....and there's more that I could carry on about that ive picked up on, but no time for boring spy/ hack info,just find this chat and text thing and only differences being in HIS OBLY, WEIRD and would love to know how and why!!! Thanks!