A “nurtured interest” can become a “hook” when it fills an institutional need. So can geographical diversity and/or musical talent.
A “spike” shows passion for a given subject (e.g., the STEM kid that has done significant research and or has consistently participated ECs related to the area of interest, or the humanities kid that has learned 4 languages, interned in museums, and/or has published his/her original writing). Your course work, summer activities, ECs, end electives will generally highlight your “spikiness.”
A “spike” becomes a “hook” when the areas of interest and the student’s passions are of potential interest to a professor for his/her research or they are done at a very high level of achievement (e.g., the aforementioned STEM kid winning an INTEL award or attending RSI or the humanities kid attending TASP or getting a highly sought out internship). Sometimes, but not always, a coach, a department, a conductor of an orchestra and/or a director, etc. will lobby for the kid. Then the spike serves as a hook.
Other hooks can involve overcoming adversity (or helping others overcome adversity), as well as the aforementioned “hooks by nature” such as those described by @TiggerDad.