1. 同位语。NOUN + active verb
Harry Potter used patronus spell, a defensive charm that can summon powerful guardians.
Eddard Stark wrote down Robert Baratheon’s last will, a formal document that makes Eddard Stark the prince regent.
Noun 经常是指某一个东西，如果是抽象（meeting/phenomenon）的话，修饰前面整个时间。
2. 同位语. Noun + prepositional phrase
Harry Potter used patronus spell, a magic for self protection.
3. 同位语. Noun + past participle
被动的时候。Harry Potter used patronus spell, a summoning magic that were been widely practiced by powerful wizards.
考点：9：00
https://www.youtube.com/watch?v=p8Agfwg9Y-Q
>>S1+V1+O1,主动用that [xxxxxxxxxxxx]
>>S1+V1+O1, 被动动用 pparticiple
Harry Potter used patronus spell, a defensive charm for summoning guardians.
Harry Potter used patronus spell, summoning a defensive guardians. 意思是不同的。
第一个是概括或者是解释前面 spell，后面指的是 修饰整件事 HP used spell, 有因果差异。
capripopcorn.com 