Basically. The idea is that your normal ways of handling things (strongest functions) come up short and can't solve a problem/situation. The extreme stress leaves your mind frantically looking for a new option, and you use functions that you hardly ever deal with (weaker functions a.k.a. "shadow" functions?). So your personality is turned upside-down, kind of...
Can someone possible explain the whole theory of "shadow functions" to me, and possible what it means for an INTP?
Whose shadow theory? The details differ depending on which interpretation you refer to.
Shadow functions are, in general, those one tends to use unconsciously and ignore when operating normally. In fact, the functions can become more likely to malfunction when too much attention is paid to them, than when they are allowed to function unconsciously and as a supplement to your stronger functions.
According to one model, one begins to manifest negative, distorted characteristics of the opposite type under stress or illness. In an INTPs case, this would be ESFJ. In practice, this means an INTP shows immature Si and Fe characteristics under stress. Note that these traits are normally shown by projecting them onto others while failing to recognize them in oneself, rather than in a simple, direct way.
According to another model, the first four functions are conscious functions, and the other four are unconscious. Therefore an INTPs shadow in this system would involve Te, Ni, Fi, and Se, and thus involve a mix of negative/destructive NTJ and SFP behaviors. Again, there's usually a degree of projection and denial associated with the shadow.