BBT help?

Amber • 7/1/09 miscarriage (8w2d), 5/31/10 my son was born, 5/26/15 chemical, 6/24/15 chemical.
I'm so new to having a hard time with TTC, I have no clue what tracking my bbt does. With our son we got pregnant right away, and now we are going on 6 months of trying. I just downloaded the app, so I've just started tracking my bbt, but what exactly am I looking for? My temps so far are under 97, I'm leaving the thermometer at my bedside table and taking it as soon as my alarm goes off in the mornings.