The basal number is the number of calories your body will burn in a resting state. Also the magic number to stay out of starvation. There are variables involved though. You see, since you are not in a resting state, you should be able to lose at that level because your daily activities will burn more than that. However, by the same token, if you work out alot, you will need to eat more to stay out of starvation mode because you will be burning ALOT more than that.

For me, Fitday has taken all the variables out. With the info you plug in, it tells you your basal levels, with the food you put it, it shows you calories in and then based on basal levels, lifestyle and any activities you enter, it tells you calories out. VERY INFORMATIVE (IMHO)

I hope if I am wrong on any of the above someone will correct me, but that is the info I got from my research on the subject.

Good luck!