Road signs and markings are the law written on the road. Section 119 of the Motor Vehicles Act requires every driver to obey them, and the shape tells you the type at a glance: circles give orders, triangles give warnings and rectangles give information.
This section explains mandatory, cautionary and informatory signs, lane lines, stop lines and painted islands, following the Indian Roads Congress codes IRC:67 for signs and IRC:35 for markings. It also covers railway level crossings: slow down, never overtake, and never enter once the barriers start closing or a red signal shows. The knowledge test includes picture questions on these signs.