The name is literal: fresh squid is dried through a single day of sun and then stopped, rather than dried hard the way ordinary dried squid is. What survives is moisture and chew, and a sweetness that fully dried squid loses.
The usual treatment is charcoal, then tearing it into strips to dip in chilli sauce or green chilli salt. Because it is still moist it will not keep at room temperature — if it is going home as a gift, it needs to be frozen.
It is also a product that attracts poor imitations. The real thing is an off-white cream colour with a thick body that gives under a finger; squid dried too long or treated with additives looks unnaturally white and feels stiff.