Ti is the fascinating and frustrating tertiary function of the INFJ. Fascinating because, when developed, it can lead to amazing realizations about things. Frustrating because, since it’s an introverted function, these realizations can be hard to explain to other people.
The main difference between Te and Ti is the external/internal factor. Te-users like graphs, methods and logical steps and outcomes. Ti prefers developing it’s own methods and systems and doesn’t necessarily always find things like graphs or processes helpful. Think of Te as the “scientist” and Ti as the “philosopher.” Ti can appreciate science, but at times still be skeptical of it.
Since Ti is internal, and not one of the top two functions of the INFJ, it can make it really difficult for INFJs to express an internal process to others, even if it makes complete sense in their heads. However, since Ti seeks precision in communication, we are usually able to explain an idea clear and concisely once we have had time to process it.