So, the "f" word could stand for 'flower', or for something way less savoury, but what Im talking about here is "f" as in f/2.8 or f/5.6 or f/11 etc etc.
More details on this coming soon elsewhere on the site but essentially the f-number of a camera lens is the ratio of the lens focal length to the diameter of the aperture. The explanation behind this can get technically complicated, but we don't do complicated here!
The 'f" number is also known as the focal ratio, f-ratio, or f-stop, and is very important in photography non more so than in flower photography.
A small number like f/1.8 or f/2.8 etc means that the lens has a very wide aperture and this means you get a very narrow, shallow depth of field in your image - perfect for taking dreamy pictures of flowers.
(A larger number as in f/11 or f/18 means that the aperture of the lens is much smaller and this means that much more, if not nearly all, of the image will end up being in focus).
So basically, all you need to remember is that the smaller the 'f' number, the bigger the aperture of the lens and the bigger the aperture of the lens the shallower the depth of field of your photography. A shallow depth of field means just a small part of you image will be in focus leaving the background to be nicely out of focus.
There is no particular magic to getting a beautiful, dreamy random background. You just need to take some pictures with the aperture wide open, experiment and let the magic begin!