You have seen the carpet like mat of flowers in the spring adorning a bank or slope. The plant was probably Spring Phlox (Phlox subulata). Sometimes called creepiong phlox, this low-growing species which forms a carpet-like mat no taller than 6 inches. This popular little perennial is best utilized in rocky areas, on slopes, and in flower beds. Creeping phlox is a versatile, easy to grow groundcover for full sun. Gritty, slightly alkaline soils are preferred and good drainage is essential. It's a good idea to shear this plant back and clean up any dead foliage in early summer, just after it's finished blooming. This will produce denser foliage and will encourage it to rebloom.