Drag Handles can be switched on or off using the 
button on the edit bar of the Select and Drag tool. Their size can be configured in Options > Environment > Cursors.
There are presently three styles of drag handles, as follows:
- Square - generally displayed at the end points of arcs and lines; at arc centres; at the corners of bounding boxes generated by text entities, graphics and filled areas and Bezier and dimension entity control points, dragging one of these handles will cause only that point to move and associated entities will be transformed accordingly
- Triangle - generally displayed at entity mid-points and symbol or block insertion extents, these handles cause all selected entities to be moved by the same amount
- Diamond - only displayed on the leader lines of angle and linear dimensions, these handles allow the dimension line positions to be moved
However, if the Move entities 
option is switched on, then all of the drag handles will be triangular ones.
Switch on the Leave original 
option to create a copy of the selected entities when dragging, otherwise the original entities will be edited.
Relative and absolute mode
There are certain situations where the Select Drag tool will replicate changes that are made to one entity using its drag handles to any others that are selected. The two modes for this replication are relative and absolute, which are controlled by holding the Shift key down whilst using the tool (after selecting the handle without holding the Shift key down).
For example, if you have more than one linear dimension selected, using the drag handle for the leader lines on one of the dimensions causes the other dimensions to be edited as well, by amounts relative (if you want to keep the leader lines at the same relative length) or absolute (if you want to make them all the same length).
Four Linear Dimensions selected - showing Drag Handles
Dimensions being dragged in Relative mode
Dimensions being dragged in Absolute mode (Shift key down)
Similarly, if you have two circles selected, using the drag handle for one will affect the other. In relative mode the same change will be made to both radii, whereas in absolute mode the two circles will be given the same radius.