Section 509 provides that those who intend to insult the modesty of a woman by words or gestures or sound or by showing any object shall be punished with simple imprisonment of maximum 3 years and fine.
This section is different from section 354 which punishes the use of force for outraging the modesty of a woman.
The acts like teasing a girl on road, passing ugly comment, making dirty signs etc. would be covered under this section.