This is a combined amount of likes from NPCs and other players online.
Every story mission and standard delivery gives likes.
These a broken down in to cargo condition as well as distance traveled and other contributing factors.
Timed deliveries are even better.
Picking up lost cargo gives +1 like and delivering them alongside standard orders generates even more (they must go back to the person you picked it up for) otherwise you get next to no likes and it just gets passed on to another player to deliver.
Contributing to road repairs gives +30-60 likes depending on how much you contribute and how many other players have put Metals/Crystals/Ceramics in recently.
Being the one to finish the repairs also generates more likes. Once repaired, for every person that uses that road, you get likes.
Building a network ot Generators is also a good way to generate likes, mixing it up from roadside and footpaths. This is because you gain likes from people using it and people are likely to give their own likes (via their touchpad) on top of it if it's a very strategically placed generator.
Showing routes for other people via signs is a good way to generate likes as people are normally very appreciative of this.
Everytime someone uses a path you used to complete a delivery or raid on a terrorist camp will also generate likes.