Sorry for such a basic question, I am starting out. I wanted to know if you can refridgerate cakes covered with fondant and decorated with fondant and/or gumpaste decorations? My concern about needing them to be cold is because of the buttercream frosting and filling. Do you need to refridgerate cakes covered in fondant with a buttercream layer of frosting underneath and in the filling (assuming the buttercream is made with real butter and not crisco). Some general guidelines on buttercream and different frostings and refridgeration would be great! THANK You!

Buttercream typically does not require refrigeration, even when made with butter. (Lots of folks on here will likely jump in with the scientific reasons, I'm not 100% sure myself! MANY experts on here that are so helpful!) but the basic reasoning I believe is that the sugar to fat ratio is so high that the sugar preserves the butter. (Some people don't refrigerate their butter at all, like leave it out on the counter all the time...so why not buttercream?
As for the fondant, I'll leave that to the fondant experts!

you can refrigerate fondant but it is not necessary to do so. It can sweat once you take it out and cause it to be gummy.

If it's just an american buttercream, you are fine with it out of the fridge. If you venture into fillings or icings that are perishable, you most definitely can refrigerate fondant cakes, and many of us do it all the time. All of my cakes have perishable icing and filling, so all of them go in the fridge.

American buttercream is butter/shortening based with powdered sugar. Other buttercreams include Meringue icings, like Swiss, Italian and French which are egg white and sugar based with butter. They need to be refrigerated.

Other fillings that need refrigeration include freshly made fruit fillings, curds of all kinds (like lemon curd), pastry creams, etc.

I personally refrigerate all my cakes because it's what I'm used to doing. The only time I had a problem is when I refrigerated a cake back in San Francisco.

I never refrigerate my cakes. I don't use perishable fillings and I always use Indydebi's buttercream. It is very hot and humid where I live several months of the year and humidity and refrigerated cakes aren't a good mix.

I always refridgerate as well - because I only use perishable fillings and frostings. We have a totally different cake culture here in Scandinavia - it's not about the cake, it's the FILLING that's important My ratio to cake and filling is 50/50. Try building tiered cakes with 50% mousse inside................I so wish I could do cakes with just a spread of buttercream or jam inbetween but no one would eat it.
But to answer your questions - ganache and american buttercream can be left in room temp as far as I've learnt here on CC.

I always refrigerate because I use perishable fillings, but also because the health department doesn't like it when you leave cakes sitting out.

Ok so it seems like most people refrigerate. So how many of you that refrigerate use fondant? And any tips when refrigerating a fondant covered cake?

When you take a fondant-covered cake out it will get wet-looking and sticky if there's a big difference in the humidity outside (it doesn't happen as much in the winter.) Just don't touch it, let it sit for a while and it will dry out when the cake comes to room temp and the temp/humidity levels equal out.