In Timeline mode, clips can be dragged left and right and move them earlier or later in the timeline, or up and down to move them to different tracks.
When either end of the clip being dragged is near either end of another clip, or the start or end of the sequence, it will "snap" to that position. Hold down the Shift key while dragging to temporarily disable this behavior.
When moving a clip so that its left edge is inside of another clip, that other clip will be split and the clip will be inserted at that point. Hold down the Alt key when dropping the clips to temporarily disable this behavior.
In Storyboard mode, clips can only be dragged left and right, to move them before or after other clips. Clips on the same track will be automatically moved to make space for the clip(s) being dragged, meaning they won't be truncated or deleted. However, clips on other video or audio tracks, which aren't visible in Storyboard mode, may be affected.
In both Timeline and Storyboard modes, linked or grouped clips will move together.