Sightings

The Sightings tab shows which Pokémon are nearby.

All the nearby Pokémon are shown with grass icons. The same type of Pokémon are grouped together. (For example, instead of showing multiple Rattatas in the area, there is only one Rattata icon in the locator). If the Sightings tab is empty, you can open it then tap the "No sightings yet" message to force refresh the list.

Updates
This tab was  previously known as Nearby. This was changed with   v.33 update. Nearby became the name of the beta tracker system, only available to select users.

There used to be footsteps which showed a trainer's proximity to the Pokémon, but that was removed in the v.31 update.