It is a species of grass known by the common name.
It is native to Brazil and Argentina, but it is known throughout the world as an introduced species and at times a common weed. Its rapid growth and spreading rhizomes make it an invasive pest in some areas.
How to get rid of:
If your weeds regrow, then you have a persistent root that you need to dig out. Use a spade or digging fork to dig up persistent weeds by the roots. Remove as many root pieces as you can.
While weeding, hold the trowel vertically (like a child holding a crayon) to eliminate strain on your wrist.