There can be much ambiguity over the difference between INTPs and INTPs, possibly because these two personalities are frequently touted by personality description websites and typology communities as two such "types". Yet these personalities differ significantly; an INTP tends to make connections among seemingly disparate ideas quickly while an INTJ prefers keeping focussed on one subject at a time and is more susceptible to new possibilities being presented than an INTP would.
INTJs on the other hand tend to be quick in their assessment of what's most effective in any situation, making decisions quickly and efficiently. They take great care in considering all their available options when purchasing something - such as gas mileage, maintenance records and features before making their final choice.
Introverted Thinking (Ti) is their dominant judging function, so INTJs tend to enjoy reading between the lines and connecting dots. They frequently imagine different scenarios and can often foresee how things will play out with great accuracy. Their secondary function, Introverted Feeling (Fi), makes them sensitive to others' feelings while caring and generous; however, their tertiary Fi may cause them to overlook any emotional consequences of their own actions.
INTJs tend to thrive when immersing themselves in intellectual or creative pursuits while having time alone. To feel fulfilled and authentic in relationships, they require friends who understand their need for privacy and authenticity - these friends should typically remain quiet but occasionally burst forth when provoked - INTJs prioritize truth and fairness but can sometimes be inflexible or stubborn in their views.