Quick answer
A self-extinguishing (flame-retardant) wire is one whose insulation stops burning on its own once the source of flame is removed, instead of continuing to burn and spread fire along the cable. It resists ignition and does not propagate flame.
This is the core idea behind FR, FR-LS and HR-FR-LSH grades. It is different from fire-resistant cable, which keeps a circuit alive during a fire. Premium house wires combine self-extinguishing behaviour with low smoke and zero halogen.
APAR Anushakti HR-FR-LSH and Fire Protekt wires are self-extinguishing and low-smoke.