You tap R1 once to say you're heading to that point, twice to say there's an enemy spotted at that location. Hold it down to bring up a radial with all sorts of shit, like I'm looting that building over there.
It gets sexual when you can shout out that there's some decent weapons/armour at this location by looking at it and pinging.
It gets transcendent when you ping the weapon in your inventory and let your squad know you need that type of ammo.
Obviously most of this is far easier with coms, but it's nice to have an option to get the message over to the shy types.