VidCutter is an easy-to-use open-source tool for trimming your videos.
Import a video and it's displayed in the preview area. You're able to drag the playback position to any frame in the film, fine-tune it with the keyboard or mouse, and play the movie at any point to confirm you've found the right position.
Cutting videos is straightforward. Choose your first frame, click "Clip Start"; choose your last frame, click "Clip End", your first clip is defined and displayed in a right-hand sidebar.
You're able to create further clips as required. Each one is added to the Clip Index sidebar, and clicking any of these later allows you to view it again.
The individual clips may also be dragged and dropped to change their order. When you're happy, click "Save Media" and VidCutter combines your clips and saves them as a single MP4 file. There's an option to keep the individual clips as separate files if you prefer.