Yarn over – you loop the yarn over your needle to make a new stitch that shows up as a little eyelet in the knitting. Common in lace knitting, very easy to forget.
I’m guessing anything with 300 stitches and lace would have to be a shawl, unless you’re mad enough to knit a lace sweater out of very, very fine gauge yarn. (I knit a sweater out of fingering weight yarn once, not a lace sweater, but I do think I was a bit mad to do it.)
Ah, I see – it’s a 2-word term where it should be a compound (yarn-over). In Russian it’s a one specific word, накид, means the same thing.
I, too, once made a sweeter with lace designs (again, the term is somewhat misleading; lace technically is not done by knitting on needles, it’s a textile category. Russian term [derived from French, I think] for needle-knitted lace is ажур, ajour – see why it is so difficult for me to grasp American knitting terms? I gave up and don’t even try to read knitting patterns in English)
Although the openwork was only in the front; it formed pattern of vertical branches with leaves, like vines – and yes, it was made with very thin yarn. Not 300, but probably 120-140 stitches wide. My mom loved it and wore it for many years.