I am cooking chicken tonight and the recipe says to cook the chicken in a cast iron skillet, well I don't have one, will just a ordinary pan work? I am just learning how to cook, so I don't know to much!
The answer is that it depends. Is the recipe for the stovetop or for an oven? If it is for an oven, make sure that your pan is oven safe to the appropriate temperature.
While your recipe will likely work fine with a normal pan, it won't develop the same kind of crispy exterior that it might with cast iron.
If you don't have a cast iron pan and aren't willing to buy one today then use what you have. Even if it doesn't work as well it will be better than not making anything.
Cast iron pans are a joy to use. With a proper season they are also as slick as the best non-stick surface and a lot less fragile. They have a ton of metal and while they don't necessarily heat evenly across the surface, they store a ton of heat in them. This means that they are particularly good for searing meat.
If you want to use a non cast iron pan, use the thickest pan you have that will hold on to the most heat.
Then go buy a cast iron pan- or inherit one from your grandmother- for next time.
The benefit of cast iron in this situation is heat retention and distribution. A big heavy steel pan will work fine, but don't use some thin teflon piece of junk.
Also, what justkt said: If it's an oven recipe, don't put a pan with plastic handles in the oven.