anything, everything, all at once

tact    consideration in dealing with others and avoiding giving offense
tactful    having or showing a sense of what is fitting and considerate in dealing with others
tactless    lacking or showing a lack of what is fitting and considerate in dealing with others
tactility    the faculty of perceiving (via the skin) pressure or sensation 
 
Tact demonstrates how thoughtful, professional, and competent a person is. 

Diplomacy is the art of dealing with people in a sensitive and tactful way.

Tact is the art of making a point without making an enemy. ~ Isaac Newton
Diplomacy is the art of letting somebody else have your way. ~ David Frost

Tact and diplomacy are methods used to aid effective communication, especially during negotiation and when attempting to be persuasive or assertive. 

the notorious catch-all 'whatchamacallit' placeholder

Imagine a former Ukrainian soldier - a young man recently discharged from the frontlines. 
While recovering from his injuries he meets, falls in love, marries a girl from the Philippine islands. 
They decide its best to return to her hometown for now and start their life there together in her barrio.