Portland cement
The standard hydraulic cement used in nearly all US concrete, sold in types numbered I through V that differ in sulfate resistance, heat output, and early strength.
What does portland cement mean?
Portland cement is a generic product name, not a brand, and it has been the default binder in American construction for well over a century. The type numbers reflect chemistry adjustments made at the plant: some resist sulfates in soil and groundwater, some generate less heat in massive placements, and some gain strength faster. Most residential and commercial work uses the general-purpose type without anyone specifying it.
In practice
You will see the type called out on a batch plant mix design or a structural drawing, usually only when soil sulfates or a cold-weather schedule made it matter.