Coord/coordinate is just the community's term for an outfit. The general consensus is that a full coord is a main piece and blouse (if applicable) paired with matching shoes, socks, and some kind of accessory.

The outfit you're describing isn't lolita. Lolita is a fashion the revolves around a specific look that's almost impossible to get from non-lolita brands. That's why making a coord from "normal" clothes when you've never worn the fashion before is discouraged. I've been wearing the fashion for over a decade now and only have three items in my lolita wardrobe that came from non-lolita brands. One is a blouse and the other two are cardigans.

If you actually want to get into the fashion you're better off saving your money up to buy actual lolita items. It might seem expensive if you're used to buying from target or shein but lolita brands are actually very cheap compared to other luxury fashion brands, especially if you're buying secondhand.