Select objects on Autocad command line
"Select objects" is a common appearance on the Autocad command line in many different Autocad commands.
It means that you have to push the enter key to finish your selection of objects. So if you have invoked a command first, such as erase, then selected the objects you wish to erase, you should actually erase them by pushing the enter key or the right mouse button.
You can of course select objects without going into a command first. Then you will see blue grips. Typing E, the short cut for the erase command or the delete key, will delete them. However the problem with this method is that you will erase all gripped objects. Even those you have gripped and forgotten, which may be out of view.
If you are using grips, always use the escape key after you have finished with them. When you start another command they will disappear. However they won't go with commonly used mouse pan and zooms. You have been warned!