It creeping sedum. You can remove small infestations of creeping sedum manually. Pull by hands or use a garden trowel to dig up and remove the plants by their roots.  Any piece of the plant that is dropped may start to grow roots. Dispose of sedum in a garbage can after manual removal. If the plant is growing with your lawn grasses, herbicides that contain 2,4-D, dicamba, MCPP, MCPA, triclopyr or mixtures of these active ingredients can provide some control. Repeated applications will be necessary. Herbicides that contain glyphoste (Roundup, others) may be the best choice for control of large, established patches. Remember, glyphosate is non-selective and will also kill any desirable grasses present.