1) What you're looking at is most likely Tongue-and-groove subflooring. No, it's not a finished floor.
2) Who knows what's sandwiched between the 'layers'. If there's some sort of duct or vent work that comes UP through the kitchen floor, then if you can remove the 'cover/grate', look at the layers that way.
3) The T-and-G is 'older' technology. Sheet suf-flooring is a cost-saving measure and just as durable.
4) Personally, I don't like tile. It's cold in Winter, pretty-much anything you drop on it breaks AND chips the tile, the grout always inevitably breaks loose, and it really raises the floor up because of the 'layers' that are necessary to make it a solid floor. More - Personally, I like tile but only where there's a STRONG joist and sub-floor system in place AND where I can use a Warm Floor System with it. The WFS is where flexible piping is run UNDER the floor (between the joists in your case), then insulated, then thermostatically controlled to keep your feet warm. Usually, I recommend sheet vinyl for kitchen flooring. It wears well, feels 'soft', is warm because it's vinyl and it heated by your feet, and relatively inexpensive to install and replace. The kitchen is a HEAVY user of foot-traffic. It's easy to clean and maintain. Idonno, tile and grout is nice in the bathroom and such because of the kind of room it is. And there, I cover it with vinyl rugs! (Go figure.) It's just my $.02. OThers will differ.
My best to ya and hope this helps.
Jay J -Moderator
PS: God Bless America
PPS: Armstrong's Solarium line is nice. It's a vinly whose patterns are NOT just 'embossed' on the suface where they'd just wear off. I don't know the name of the process they use but the pattern is called a Wear Layer, where the pattern is 'deep' in the vinyl and wears equally w/the vinyl ...