I am a complete novice with lightroom. There does not appear to be a faciility to use layers or layer masks. Is this correct.?
There are layer masks in Lightroom. They simply appear in a different form than in Photoshop.
For example, if in Photoshop you would have applied a Saturation adjustment layer and restricted where it applies by painting in its layer mask, in Lightroom you would use the Local Adjustment brush set to Saturation and paint in the adjustment in a similar way. But if there's no Layers panel, where's the mask you painted in Lightroom? Press the O key and you'll see the mask overlay (Tools > Adjustment Brush Overlay > Show Overlay), similar to when you press the backslash key in Photoshop to do the same thing. You can add to or erase part of that mask, just as in Photoshop. Instead of a stack of layers you see multiple adjustment pins on the image, and each pin has a mask associated with it.
One thing novices run into is the assumption that the Photoshop interface represents the best and only way to do things. But Photoshop was designed in the 1980s, an era of film scans, print output, CMYK, and slow computers. Some parts of Lightroom attempt to rethink editing in terms of today's digital photography and raw files to see if there's a better way.
I was given to understand that ALL editing/improvements were capable in Lightroom, and that this programme was aimed specificaly at photographers.
No, Lightroom doesn't completely replace Photoshop, it complements it. Technically, Photoshop has several times more features than Lightroom does, but it isn't just about how many features it has. The reason you hear about a lot of photographers with deep Photoshop experience now doing most of their work in Lightroom is that they work mostly with raw files, and they have found (as I have) that importing, editing, organizing, and printing large shoots of raw files at high quality is much more efficiently integrated in one program (Lightroom) than in three (Camera Raw, Bridge, and Photoshop). Many photographers now try to do as much editing as they can in Lightroom for its bulk editing efficiency and non-destructive editing, only going to Photoshop for jobs that Lightroom can't handle like compositing or pixel-level editing.
Also, because of the way Lightroom edits using metadata, if you apply a lot of adjustment masks for contrast, sharpness, etc. those changes will take up a very small amount of disk space compared to a Photoshop document containing the layers and masks required to achieve the same results.