Ovens generally convey heat too slowly to be ideal to pop popcorn to understand why let's get into the science of how popcorn pops.
Popcorn pops that the boiling point of water inside the kernel at popping pressure. This is NOT 100 degrees Centigrade or 215 Fahrenheit. That is the boiling point of water at sea level air pressure (i.e. 1 Atmousphere pressure.)
The steam needs to reach much higher pressure to burst the kernel open, and thus needs a higher temperature to create steam to the pressure. (much like inside pressure cooker.) The pressure needs to reach roughly 135 PSI (~9 bar), or 9-40 times the pressure of a consumer pressure cooker (depending on model and design.)
The temperature at which this pressure is reached is roughly 180-200C or 350-390F. Yes, these numbers don't match up, they are just the nice round numbers referenced.
You may note that the temperature is well over the smoke point of butter, yeah, don't use butter. If you like butter, you'll have to use clarified butter, and the stuff you clarify yourself probably won't be good enough unless you are a 5 star chef so you'll have to buy the fancy stuff. Butter can go on afterwards as a flavoring.
Back to the point, as of why popping in the oven doesn't work well, you CAN pop popcorn in an oven, but that doesn't mean it's advised to. An oven will heat the oil too slowly, and thus heat the popcorn too slowly. The result of this is the steam escaping before it reaches critical pressure, and getting a lot of old maids, meanwhile the popped popcorn will spend too much time at cooking temperature and fry in the oil or otherwise cook and burn. Hence you will get a lot of burnt popcorn. It just doesn't make good popcorn.
The method I prefer is using an induction burner or some other thermostat controlled burner. However, you can use an oven burner (electric or gas) if you don't and use medium heat taking care not to burn the oil, and thus ruining all the popcorn.
For a cooking container I like a stainless steel bowl, other people prefer an enamel steel pot or cast iron. You need a lid, but if you don't have one, Aluminum foil is always a good substitute. Have a second container of roughly the same volume, or slightly bigger ready to pour the popcorn into.
There are two different preferred methods here, just use the one that works for you.
If you want to preheat the oil, which works best with larger and heavier cooking vessels heat the fat you like to it's cooking temperature (maximum temperature under the approximate 215C/420F where the starch will start burning way too easily, and smoke point of your oil, whichever is lower. I use 190C/375F myself, which works fairly well. When the oil reaches temperature (as determined by a thermometer, or your preferred method. You can always throw in a kernel to check. It should pop in a few seconds.)
Once the oil is ready you should throw in the kernels, enough to layer 3-4 layers over the oil, or enough to pop the container full of popcorn, whichever is less (obviously).
Throw the lid on, and shake the container periodically on the burner to keep popcorn from being stuck. Once the popcorn slows, or the container lid is being pushed off, pull it from the heat, and dump out the popcorn goodness.
To do the non-preheat method you need a powerful burner, a smaller container, and/or a thermostat controlled burner. Preferably all three. You throw the popcorn in at the start and heat like before. Shake it every 30 seconds or so until it starts to pop, then continue as before.
After you are done cooking the popcorn, add your favorite flavorings, be it fake butter flavor, real butter, salt, caramel or any of the more exotic flavors out there. There is Coco, Hot Pepper, Balsamic Vinegar, Malt Vinegar, fish oil, peanut butter, garlic, pesto spices or whatever suits your taste, there's plenty of crazy toppings out there, and if you ever run out of ideas you have a whole world of information online to find more ideas on. You have to love the information age.
As for an additional tip My favorite two fats are peanut oil and high-grade refined clarified butter. Since clarified butter is more expensive in the US, being a specialty product mainly bought by hipsters looking to impress their date and peanut oil is dirt cheap oil bought by us worker drones who like to fry our own fries at our BBQs, I tend to use peanut oil unless it's a special occasion. I hear that in Europe and Asia clarified butter is easier to get a hold of for a decent price. I don't know if that's true, but it might be good.