Setting a clip’s In and Out points is a process called marking. You define the first frame you want to include in a sequence by marking that frame as the clip’s In point. Then you define the last frame you want to include by marking it as the Out point. In a typical workflow, you mark In and Out points for a clip in the Source Monitor.
Adjusting a clip's In and Out points after it is already edited into a sequence is called trimming. Typically, you trim clips to adjust how they play back in a sequence. For example, as you view the edit, you decide that you want to cut to the incoming clip a little sooner than you originally planned while marking clips. To fix that problem, trim the clip using trimming tools in Premiere Pro.
You can trim clips by dragging the edge of a clip. A clip's "edge" is a clip’s In or Out point, or edit point. Several specialized tools and techniques allow you to trim an edit point. These tools and techniques allow you to trim more easily and accurately, reducing the number of steps involved and maintaining the integrity of the sequence.
You can fine-tune trim edits in a sequence in the Trim Monitor. The Trim Monitor’s layout is similar to the Source and Program Monitors, but the Trim Monitor controls are optimized for precisely adjusting a cut point between clips in a sequence.
You can trim clips in the Speech Analysis pane of the Metadata panel, setting In points and Out points on selected spoken words.