No Stupid Questions

Well, there's a number of reasons for the shape of the various bread types. The dough type - from the kind of flour used, through the resting time, fermentation time, raising agent (let it be any of a variety of yeast products, wild yeast aka sourdough starter, baking powder or baking soda, there's tons of options), how hydrated it is, and so on. The oven type and baking approach. The purpose of the bread.

Your first picture is of a standard toast or sandwich bread. It's supposed to be a fairly loose, soft bread with a soft crust and an engineered shape for easier baking - with conduction baking on all sides except the top (here conduction baking refers to the fact the sides and bottom of the bread is held in place by a heated metal tray, transferring heat directly without letting air or steam escape, resulting in the soft crust). A more industrial yeast type is used (usually dry or instant yeast), which result in relatively small gas bubbles, giving it a dense but fluffy interior. The flour is usually a light wheat flour, and both resting and fermentation times are low - that's why it's a more industrial bread, you mix the ingredients, let the mixture sit for 30-60 minutes then bake it, easily automated.

The second picture is of a sourdough loaf. This usually uses wholemeal wheat flour, often mixed with rye or other grains for better texture, and is a fairly tedious bread to make with multiple stretch and fold sequences and long resting periods, allowing lots of gluten to form, which means every stretch and fold sequence doesn't mix the dough but rather layers and shapes it. The yeast comes from a sourdough starter, and is allowed to ferment longer, which is why you get an intense flavour. It bakes quick in a Dutch oven first covered then uncovered, allowing it to fluff up but then shape a hard crust. You get much larger bubbles and an internal structure of long strands of gluten forming swirls and such.

Then the baguette, it uses a different approach to sourdough but with a similar effect. Unlike sandwich bread, the dough for baguettes - as well as what I'd call "European medium bread" (medium here meaning the hardness and bakedness of the crust) - a crispy crust that isn't as well baked as a sourdough, but also isn't soft, with a well developed gluten structure, using more predictable yeasts (again usually instant quick yeast or dry yeast, or in some areas, live yeast cubes). Mind you the baguette you're showing is more of a hypermarket style baguette that is intentionally baked to a lesser darkness, and traditional baguettes are more on the golden brown part of the scale.

Overall, the kind of flour determines the flavour, but also the raising and resting times. Some flours (especially wholemeal or grain mix flours) need more time as the more complex proteins and sugars take more time to be broken down by the yeast thus they rise slower. Hydration determines how tough the dough is to shape (e.g. pasta is only hydrated by the eggs, making it a hard, dense dough, pizza needs to be flexible so it's high hydration, and it gets extra raise in the oven as the water quickly evaporates). Yeast determines the flavour, the raising time, and in the final product, the texture and airiness. The baking method can fuck a lot with the texture. A regular convection oven can dry the crust out making it tough and thick, forming quickly and stopping the bread from rising, but adding some ice in a pan at the bottom can generate enough steam to let the bread rise properly by delaying the crust hardening. Same idea for sourdough using a Dutch oven, you create a high moisture environment, a steam box, to keep the crust soft while the bread rises, then remove it at the end so the crust can cripsen and brown. The sandwich bread is medium hydration thus it keeps the sides moist while they bake, giving it that brown but soft crust. If you were to plop the same dough just into the oven, without the baking shape, due to there being little to no gluten development, it would just fall apart and harden into the world's shittiest giant cookie.

But also you can bake bread in a Dutch oven over an open fire, giving a more rustic style bread with thick, chewy, but also cripsy crust. Toss the same dough with lower hydration into a circle and onto an upside down pan in the same fire and you got some awesome flatbread with a nice center air pocket you can open up and stuff with meat.

Then, you can decide to just fuck it and add as much high fructose corn syrup as possible without fucking up the bread, and you get American style bread.