Adobe Lightroom's user interface is very streamlined and easy to use. It consists of panels on the left, right, top, and bottom of the screen, all of which can be collapsed and resized if needed.
The top panel lets you choose different modes:
The left panel differs slightly between the different modes, but generally it is the panel you would use to navigate through different folders and collections. Also, this panel is used to view the history of the photo (the changes you have made to it). The left panel also shows presets for effects and adjustments to photos.
The right panel is mode-specific. In library mode, it shows settings for identifying photos. Some examples of these settings are Keywords and Metadata. It also contains basic photo adjustment tools such as White Balance and Tone Control. In develop mode, this is the panel that has all the adjustments you can make to a photo. It also has the tools such as the red eye remover and the masking tool. In slideshow mode, this panel has the settings to how the photo will be presented in the slideshow. In the print mode, the right panel has settings for paper settings such as the margins and also a watermarking tool. For the web panel, this is where you will choose what type of gallery you want exported for a website.
The sub-sections of each panel are all collapsible, meaning you are able to just view one section at a time or many sections at a time, you choose.
An vast library of plugins is available for Lightroom, both free and paid. The plugins range from export plugins for web services, to internal editing tools. For example, there are plugins for working with HDR photos.