The short answer is that “waterproof” and “water-resistant” are not interchangeable, and in urban outdoor furniture the difference usually shows up in the details rather than the label. I would start by asking what the manufacturer actually means. Truly waterproof furniture should be tested to a recognized standard or clearly rated for specific conditions, such as sustained rain or standing water. Water-resistant furniture is designed to repel light moisture and dry quickly, but it may still soak through in heavy or prolonged rain.
Check the construction before you trust the word “waterproof.” Look at seams, welds, zippers, cushion covers, and drainage. A waterproof sofa frame may have welded or sealed seams, drainage holes, and raised feet so water cannot pool. Cushions are often the weak point: quick-dry foam and solution-dyed acrylic or PVC fabric can handle rain better, but unless the cover has sealed seams and a protected zipper, it is usually water-resistant rather than fully waterproof. Powder-coated aluminum, HDPE, and marine-grade stainless steel are good signs; untreated steel and hidden joints are not.
Ask for specifics. A credible seller should provide fabric hydrostatic head ratings, spray-test results, IP ratings for covers or storage, warranty language, and care instructions. Vague claims like “rainproof” or “all-weather” mean little on their own. I also like simple real-world checks: put a few drops of water on the fabric and see whether they bead up or sink in; inspect the underside after a rain; look for water trapped in seams, piping, and cushion cores; and check whether fasteners or legs sit in puddles.
Finally, read the warranty. If the company promises waterproof performance, it should say what conditions are covered and what is excluded. In practice, most urban outdoor furniture is water-resistant to some degree, while truly waterproof pieces are engineered with sealed construction, drainage, and tested materials. If a seller cannot explain the difference clearly, I assume it is water-resistant until proven otherwise.