This plant was put in by a builder. It has a central group of grass-like blades. In year 2, it has sent out offsets and spread into the surrounding area. The smaller groups are connected to the central root system. What kind of plant is this?
That is Liriope spicata or creeping lilyturf. It differs from the big blue lilyturf (Liriope muscari) in that is forms a smaller, less dense clump of foliage, and quickly sends out underground stolons, especially in soft soil. The flowers are similar but slightly more inconspicuous. It will eventually fill in to become a solid carpet, as pictured below.