Solid Hardwood, Engineered and Laminate Flooring - What is under laminate?

I have a condo with a second story bathroom that has alot of water damage to the floor between the toilet and the shower.
I'm trying to figure out what it is I'm removing, because I'll need to replace it. Is it possible that pressed board is installed over the plywood bathroom floor, under the laminate? In the dry area it looks like flakes of wood pressed together? Any ideas? Thanks!

wood laminate (fake wood stuff) is a paper-thin photograph of wood that is glued to pressboard. is that what you're seeing? yes, you could have another layer of pressboard under there, or plywood, etc. but there should be a plastic & thin foam underlayment pad directly under the laminate planks, on top of whatever subfloor you have. do you see that?

are you replacing the entire floor or just a section?

In addition to delamination of the floor cover, water damage likely affected subfloor. Particleboard is sawdust and glue and tends to swell when exposed to moisture. OSB looks like large flakes of different types of wood that have been pressed together with glue. No matter what subfloor you have, if water damaged, it should be replaced.

Laminate flooring tends not to fair well in areas where it will be exposed to water. Considering other floor covering options is recommended.

Thank you both!
It seems from this info that I have OSB, I think I would feel better replacing the whole floor, that way I would be sure I removed all the water damage, and to be honest 75% is damaged anyway.
I haven't found any plastic or foam underlay.
I'm going to put down the OSB then those self stick 12X12 vinyl tiles. Think that would work? Do I need to lay plastic or foam also?
Thanks again

With its contifinish-surface OSB retains humidity and moisture in most cases without any special moisture-proofing treatment.

So I don't think you should put the plastic and foam under the OSB. It is just my opinion for your information.

you'll want to post how-to questions regarding vinyl tiles in the Vinyl & Lineoleum topic (though i'd recommend sheet vinyl over the tiles - water can get right in between the tiles, whereas the sheet vinyl would be better).

good luck!