[R] Difference between stats.steps() and MuMIn.dredge() to select best fit model

[c@buhtz m@iii@g oii posteo@jp]

Hello,

I try to understand the different approaches how to select the best fit 
regression model.
This is not about AIC, BIC, etc. It is about the difference between the 
steps() function
(in stats package) and the dredge() function (in MuMIn) package.
I see several examples on the internet.

step() explore the model space with a step wise approach.
And dredge() try out all possible combinations of the variables.

But isn't that the same? I might have a mental block on this.

Which model (formula) would dredge() "test" that step() wouldn't?`

Thanks in advance,
Christian