This is the default main window layout which appears when starting Kdenlive. The layout is fully configurable, but this tutorial assumes the default is being used.
Kdenlive's menu bar doesn't really respect established user interface guidelines. Instead of documenting the current layout, this section will soon link to some change proposals.
Copy, Paste etc.
A total of 8 different docking panels provide access to many of the editing tools in Kdenlive. They may be docked, tabbed, floated, or hidden in any conceivable configuration.
The Project Tree shows the video clips, images, slideshows, colour clips and title clips that belong to your project.
Effect Stack shows the different effects applied to a particular clip. In this tab you will be able to define the order in which they are applied and also parameterise them.
Transition allows editing the transitions between two clips on the timeline. Several types are available.
Effect List enumerates your available audio, video and custom effects. These can be applied to clips on the timeline.
Custom effects are described below.
Capture monitor allows you to directly capture video from a number of sources:
a screen capture (you'll need recordmydesktop  utility)
The bottom panel in the window holds the timeline. The timeline gives you a visual representation of your project, and shows when clips start, when they end, and in the case of overlapping clips, which one is actually being used. The timeline can contain multiple audio and video tracks, where you can add sound and video clips respectively and other fancy stuffs (transitions, titles, ...)
A status bar is located at the bottom of the timeline. This bar provides information about your project and also holds some useful icons.
You can use it to select the update or razor tool, zoom the timeline, toggle on/off the thumbnails for video and audio, and decide to show or not markers and snappoints. It also displays the timeline time of your cursor.
(This older image is missing the spacer tool, but there is a rendering glitch on my Kdenlive build which clips the status bar, so I went with this image)