Looks like roughstalk bluegrass, also known as poa trivialis. This is a weed grass, and unfortunately a particularly noxious fast moving one. At this time there is no herbicide that will selectively kill it and not your lawn.
It is perennial.
If you only have it in a small area, pull it or kill it with an herbicide containing glyphosate. Do so immediately, before it can produce seeds. (This is happening already for many homeowners.)
This weed is favored by wet soil conditions. Change that if you can.