Sliding changes a shot's position in the edit sequence without changing the head or the tail frames. It simultaneously slides the shot under the cursor and trims the head and tail of the surrounding gaps.
You can slide an element or a transition. See Transitions.
To slide an element:
Disable Trim.
Position the cursor on the middle of the element that you want to slide.
Click the element.
The slide cursor appears.
Drag the element right or left.