I am currently solving one classification problem using logistic regression algorithm in R .I have created the model using step function, but my step function only performs forward chaining.I want to know is there a way by which I can perform backward chaining.

`mod<-step(glm(Dependent~., family = binomial(link=logit),data = train_final))`

I also want to know what does AIC means in the model and how it values affect the model.