Factor and Lm functions

Hei,
I have a formula for a model as follows
lm(TS~log(BodyWt)+log(BodyWt):factor(D). I do not use R for programming
hence I dont understand what is the second covariate in the model
"log(BodyWt):factor(D)".
Where BodyWt = body weight and D = danger index (either 1 or 2). I want to
run the same model in other program. Can anyone explain me what is doing the
: operator and the factor() function.

Thanks

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