The document introduces the Mandarin verb "xiǎng" which is used to express what someone would like to do. It provides examples of using the structure "S + 想 + VP" where S is the subject and VP is the verb phrase. Some examples given are "我想買這個" (I want to buy this), "她想看電影" (She wants to watch a movie), and responses like "好" (okay) or "不可以" (no). The document emphasizes that using "xiǎng" is helpful for expressing what someone wants or would like to do.