What type of wood is this?
Based on the color (light; pink tinge), knots (lots), and grain (wide) I would say it's a soft wood but I don't know what type. Common soft wood flooring would be pine and fir. Soft woods can be dented with your fingernail (unlike oak, for example—a common hardwood species for flooring).

You can definitely stain pine, but that floor doesn't look stained to me. What exactly did you do?