Tereza represents purity and innocence that lead Tomas to see her as "child put in a basket and sent downstream" for him to find. Tereza is waiting for someone like Tomas to appear even before she meets him; even after she meets him, his constant betrayals mean she must frequently wait for him to return. The two love each other deeply, but make each other miserable. Tereza is not vulgar or kitsch in any easily recognizable sense; however, where Tomas and Sabina are light, she is heavy.
Tereza does not damn Tomas for his infidelities, and instead characterizes herself as weaker than him. Her "strongest" moment comes when she leaves Zurich and Tomas and returns to Prague alone, sacrificing her own happiness to relieve Tomas of the burden of her love. Precisely because of her intelligence and compassion, Tereza presents a kind of heaviness Tomas cannot easily dismiss.
Dissident activism interests Tereza. She finds meaning, beauty, and weight in her courageous work as a photo-journalist during the Soviet takeover of Prague; unlike most of the European political left, however, Tereza admits to the existence of naiveté in her political work.
Tereza changes considerably during the course of The Unbearable Lightness of Being, as she is increasingly forced to recognize the impossibility of her youthful dreams. Nothing remains as black and white as she feels it should be; Tereza even comes to admire her archrival Sabina and feels Sabina's powerful sensuality, although she knows Sabina is Tomas's beloved mistress. Just as Tomas must question his lightness, Tereza must question her heaviness.