Sorry. Here, let me put on my Professor's hat, where is the thing.......ah. Better.
Lamina is a term used to describe the part of the leaf where the stalked glands are to be found. The other part of the leaf, where there are no glands, is termed the petiole.
Both terms are very often used in describing Drosera species.
Regarding the petiole, some other terms you might run into would be glaborous: meaning without hairs. So, the term "glaborous petiole" should call to mind that part of the leaf that has no stalked glands (since these are confined to the lamina), and also no hairs. The opposite would be "hirsute" or hairy: the absence or presence of hairs on the petiole reveal much in the study of this genus.
Petioles may be straight sided, or tapering. The tapering may be gradual or abrupt. The petiole taken in cross section may be described in many different degrees as well.
In regards to the lamina, it can have different shapes. Lamina may be round (or rotundate), as in D. rotundifolia, spathulate: shaped like a baseball bat cut in half (as in D. spathulata), truncate, terminating in a straight line, as if cut off, (e.g. D. aliciae, D. brevifolia). The qualitative terms may also be combined and modified: sub-rotund (almost round) or spathulate-obovate (widely tapering baseball bat, lol), etc.
Lamina may be erect (as in D. intermedia)or D. venusta, prostrate (or adpressed) as in D. spatulata.
There are many more terms, but these are some that are frequently used. Using these terms it is possible to describe many species of Drosera, and to discuss their likenesses and differences.
Taxonomy is more than a science: it is an art! There is real beauty in someones ability to describe a plant so exactly.