For now, Becki chooses "Browse Profiles." She's chooses her prefered gender from the top two buttons, and we get a scroll box with everyone who is also signed up with the site.
Hunter looks like a winner (or at least the least drugged-out), so she clicks his picture.
Simply put, when any unrelated Sim is near your active Sims, you might see a push notification of the visitor being attracted to your Sim.
As you can see in the screen shot here, a townie is attracted to Pete simply because she caught him studying a new skill.
Other Sims don't respect your vows, so you may get a lot of calls asking your Sims on a date even if they're married.
This brings up Hunter's profile, including his traits and favorites.
Like Becki, he could be lying, but it would be a sad Sim world if we were so cynical that we just assumed nobody could tell the truth.
There is no way to turn it off (unlike opportunities), so it might get a little annoying if your Sims have particularly active social lives.
Attraction is subject to the same rules as other relationships when considering whether men or women hit on any particular Sim.
Attraction can occur for any number of reasons, though you'll likely see it most often when Sims learn new skills.