FIRO-B is a measure of three interpersonal needs :

Inclusion [I] :
A need for new relationships and associating with others and determines the amount of contact and prominence that a person seeks. It includes need for belonging, recognition, distinction, involvement, and participation

Control [C]  :
A need for decision-making, influence, and persuasion between people; it determines the extent of power or dominance that a person seeks. It includes need for power, responsibility, authority, consistency and influence

Affection [A] :
A need for emotional ties and warm connections between people; it determines the extent of  closeness that a person seeks. It includes need for personal ties, support, consensus, openness, and sensitivity

For each of the three interpersonal needs, the FIRO-B instrument also provides a measure of how much each need is Expressed or Wanted by an individual.