A proposal of marriage set to a pudding. Children sing it in a ring: one stands in the middle, the rest circle, and at con , con no the chooser points - yes to this one, no to that one - until the song ends on a choice. It was already old when a folklorist wrote it down in Asturias in 1895, and it is still sung from Madrid to Buenos Aires.
The grammar smuggled inside is the subjunctive. , - who can sew, who can embroider - is saber in the subjunctive (sepa), because the bride is hypothetical. You will meet this structure formally much later in the course; for now the song plants the sound of it, which is how natives learned it too.
The husband-hunting criteria are, admittedly, from 1895. Treat the sewing and embroidering as a period detail, like the military-style shirts in the version the folklorist collected, and enjoy the tune.