The ISI mark is a certification mark showing that a product conforms to the relevant Indian Standard set by the Bureau of Indian Standards (BIS), India's national standards body. For wires and cables it is an important assurance of quality and safety.
When a cable carries the ISI mark it means the manufacturer is licensed by BIS and the product has been made and tested to the applicable specification — for house wiring, that is typically IS 694. It tells a buyer the cable meets defined requirements for insulation, conductor and fire performance, rather than being an untested product.
Practical advice: look for the ISI mark and the IS number printed on the cable and packaging, and buy from authorised sellers — see how to check you are buying genuine APAR cables. You can also review APAR's certifications and approvals, or contact APAR with any query.