The 把 construction (把字句) moves the object before the verb to emphasize the result or disposal of that object: 把 + object + verb + result. The verb must have a complement or other element after it — you can't just say 把书看.
usage
As a measure word, 把 is used for things with handles (一把刀 a knife, 一把伞 an umbrella) or handfuls (一把米 a handful of rice).
mistakes
Don't use 把 with 有, 是, 在, 知道, or other stative verbs. It's only for actions that affect or change the object.
