Do you mean the difference between INFP and ENFP in regards to those functions, or the difference between manifestation in NFPs and STJs?
I know in me Te looks something along the lines of if Fi feels strongly about something, I become strangely organized, planful, even authoritarian. For example, if the mother cat needs to get into the room to see her kittens, I will do something my roommate calls "police knock" and it kind of freaks him out lol. It's because when I feel strongly about something suddenly I mean SRS BIZNESS. It can also shock people IRL because I'm so mellow and easy going so much of the time, can be pretty adaptable and dreamy, spontaneous, dreamy, lazy even...I procrastinate a lot, and care more about relationships and art and things like that than accomplishments. But if something triggers my Fi I'll suddenly turn into this bossy drill sargeant, like I'll seriously become Sargeant Marm and start giving out commands and saying "the logistics of this will not work!" and "this is how we're going to do this."
Basically I go from being a harmless little NF to being SUPRISE AUTHORITARIAN. It really shocks some people.
I also rely on Te/Si in survival situations, to execute Ne ideas and for a barrier of pseudo-STJ self-protection in tough spots.
My Si largely is tied into my Fi, so it principally seems to serve some nostalgic purpose for me, and helps me collect details for things I *care* about (like English literature, writing, spelling) and also shows up in the form of neurosis about health, safety, and security. I have a lot of internal bodily awareness.
HOWEVER what seperates me from an SJ is that my Si does not like to collect external detail, do detail work, or really serve much of a "useful" purpose in terms of taking care of detail in daily life, or cataloguing, or remembering step-by-step execution in doing things. I also am not very precise, where as SJs a lot of the time will be. I do not follow a linear train of thought, and jump around with Ne for the most part.