Act I, Scene iv, Lines 106-113 is not a speech by Romeo. It is Mercution, Benvolio, and Romeo talking after Mercutio gives his speech about dreams. If you are asking about Mercutio's Queen Mab speech, you may check the link below for more information.
As for those lines in particular, however, Mercutio says,
Begot of nothing but vain fantasy,
Which is as thin of substance as the air
And more inconstant than the wind, who wooes
Even now the frozen bosom of the north, (Lines 104-107).
In this section, Mercutio is discussing how dreams can't amount to reality because they are fiction in fantasy. He relates fantasy to something as thin as air and changes just as quickly as the wind does. We cannot base our life's goals upon dreams that change so quickly and amount to nothing, according to Mercutio.
Here's the link that will send you to the study guide pages.