What is the learning sign "uggahanimitta"?

In the jhana meditation book I'm reading, _Critical Analysis Of The Jhanas_, it is stated that to suppress the Hindrance, you first focus your mind on a jhana meditation object. Once you mature you will be able to see the object clearly, it will become a visual object in your mind. So is (uggahanimitta) a visual representation of my breath? Where I can see my breath flowing? Also they stated that this stage will mature the 5 jhana factors. That once you reached uggahanimitta, the 5 jhana factors start to mature and become stronger? I thought that to supress the hindrances you must change your life and incorporate the 5 factors. Sorry I'm just so lost.