If you are being quoted aluminum storefront framing for a four-story glazed elevation, stop and get a second opinion. Storefront and curtain wall are both grids of aluminum holding glass, and from across the street they look like the same thing. Structurally they are not remotely the same thing.
Storefront
Storefront is a non-load-bearing glazed system installed inside an opening, between floors, typically at ground level and typically no more than about a single story tall. It sits in the opening and transfers its load to the surrounding structure at the perimeter. The common commercial depth is 2 inches by 4½ inches, center-glazed, and it is normally assembled and glazed in place.
It is the right system for retail frontage, ground-floor entries, restaurant fronts and interior glazed walls. It is economical, quick to install, and easy to reglaze years later.
Curtain wall
Curtain wall hangs off the face of the building structure and runs continuously past the floor slabs, carrying its own weight back to anchors at each floor. It is a skin rather than an infill. It has to accommodate building movement, thermal expansion and floor deflection, and it is engineered for the wind load at that height on that elevation.
Window wall is the third term people run into. It sits between the slabs, floor to floor, rather than spanning past them — which makes it cheaper than curtain wall and common in multifamily buildings.
How water is handled
This is the real division. Storefront generally relies on a sealed perimeter to keep water out. Curtain wall assumes water will get in, and is designed to manage it — pressure-equalised chambers, internal gutters, weep holes and gaskets that route water back out of the system.
That distinction explains most curtain wall leak calls. The glass is rarely the problem. Blocked weeps, failed gaskets or a well-meant bead of sealant applied straight over a drainage path are the problem. Sealing a curtain wall leak from the outside without understanding where the water is meant to exit usually just relocates the leak.
Telling them apart on your own building
Look at where the glazing meets the floor lines. If the aluminum grid runs continuously past each floor with no break, and the elevation is more than one story of continuous glass, you are almost certainly looking at curtain wall. If the glazing stops at the head of the ground floor and the structure above is solid, that is storefront.
It matters commercially because the two carry very different costs, lead times, engineering requirements and access needs. Replacing one panel of curtain wall three floors up is a different job from reglazing a storefront, and the access equipment usually costs more than the glass.