Psionics
When you Attune, you tap into your instincts, intuition, and your sense of empathy to reach out to other people or to assess a situation. If your character is a psion, then Attuning also allows you to open your mind to the unseen world of otherspace and perceive things beyond your mundane senses. Usually this only applies if you picked The Psion as a playbook during character creation, but your table might decide that a “mundane” character awakens to their psionic aptitude based on the events that unfold in your game.
Psionic aptitude resides within every human being, though a “natural talent” is very rare. When a psion uses Attune, they’re doing the same things an ordinary human does - they’re tapping into their intuition and reaching out with their feelings to those around them. They are just unusually sensitive - usually as a result of shady experimentation, exposure to otherspace or strange alien life, or uniquely traumatic experiences. Because of how rare the psionic talent is, most campaigns should include at most one character with psionic abilities unless psionics are the entire focus of the campaign.
Psionic attunement can often be a shortcut to tasks that would otherwise require specialised skills. Why Charm someone when you can just read their mind, or Observe the situation when you can rely on your precognitive powers? But the hidden world that psionics tap into is never quite safe to take hold of. Tasks that would be relatively mundane with another specialty often have a worse position when you use Attune for them, because opening your mind to the howling void is never without risk.
When you Attune with psionics, you gain access to a sense that most people don’t have. Most psions can’t use it as a weapon against others or to move objects around in the physical world. Most psionics also struggle to reach out to non-human minds with their talents, though with training it is possible to commune with animals and even aliens.
You might: try to telepathically communicate with another creature; read the mind or sense the emotions of an unwitting person; see the otherspace echoes of recent events; or perceive beyond your senses to gain insight about your current situation.