The grid is a rectangular pattern of lines or dots that covers the whole workspace in AutoCAD. It is similar to placing a piece of graph paper under a drawing and is used to help align and visualize objects. It is only for reference and is not printed in the final drawing. Easily turn on and off the grid by clicking the grid icon in the Status Bar.
The erase command is used to delete objects.
1) Activate the the erase command by selecting the Erase button OR by type "erase" and hit enter
2) Select objects to be deleted
3) Hit enter and selected objects should disappear
Remember, there are always multiple ways to complete tasks in AutoCAD. A quicker method of erasing objects is to select the objects and hit the "Delete" key on the keyboard.