Using grips in AutoCAD can be a useful way of editing your objects. Whether you are moving an object or lengthening a line, grips can be faster than finding the traditional tools for editing.
When the grips are "blue" they are cold or not selected. When you select the grips, they turn red, or whats called "hot", which means they are active and ready for action.
In recent releases of AutoCAD, more features have been added to grip selection. For example, on a polyline, we can now edit Vertices. Which includes: adding, removing or stretching.