Definition
Trust building is the slow accrual of confidence between people that the other party is competent, honest, and acting in good faith. It is not a feeling that arrives; it is an account that fills, deposit by deposit, until it tips. The deposits are unglamorous — small promises kept, small mistakes acknowledged, small acts of consideration that no one is watching for.
Trust differs from rapport in time scale. Rapport is the everyday surface of a relationship; trust is the deep stock built up over months and years. You can have rapport with someone you have just met; trust requires a track record.
Why it matters
How it works
Trust has three components — competence (can you do what you say?), honesty (do you say what you believe?), and care (do you have my interests partly in mind?). All three must be visible for trust to form fully; missing any one creates a specific failure mode. Competence without honesty produces a polished but unreliable colleague; honesty without competence produces a sincere disappointment; competence and honesty without care produces a useful but cold relationship that no one extends past necessity.
The repair move when trust is damaged is the same as in admitting mistakes: name the rupture explicitly, take responsibility for your specific part, and let time pass while acting differently. The timeframe is months, not days.