At first glance Nuke looks really difficult to learn, with its odd interface without any apparent timeline and its node-based workflow. But as one gets use to the principle of node-based compositing, it quickly becomes a lot easier. Then... it becomes difficult again as its many nuances become apparent.
Nuke's main panes
Other interface elements
Most of the complexity of Nuke does not live in its panels, but within the properties of the many nodes within the Toolbar. Though these properties are different in each node, they share a good deal of interface similarity.
The Project Settings is where the settings specific to that project are defined. These should be set at the very beginning of your project.