I'd like to know the difference between the two. I guess a stand is fixed to the place and sells something like newspapers and drinks, and a stall is not fixed to the place and temporary. Is my understanding correct?
There is no exact rule distinguishing stall from stand, but looking at the etymology can shed a lot of light. Stall comes from older words meaning a place in a barn where animals stand, especially where a single horse, cow, or pig stands, like this:
This is still the primary meaning, usually listed first in dictionaries. Most of the other meanings are best understood as extensions of this one—even though, in modern life, most city-dwellers never see this kind of stall.
As you can see from this Google search, people make stalls for animals in a variety of sizes and configurations, but most have the following in common: they usually hold one animal who usually stands (sometimes a few animals share one stall), they usually have three walls plus a gate or a wall with an opening where the animal can poke through to access a feeder, they're usually arranged in rows where all the stalls face a path or corridor where a person can walk, and they're usually very spare and modest, serving a utilitarian purpose in a very simple way.
Market stalls, urinal stalls, bathroom stalls, shower stalls, etc. are all similar to animal stalls in obvious ways, but often they don't share all the characteristics. People usually stand in market stalls, urinal stalls, and shower stalls, but they usually sit down in bathroom stalls. As with stalls for animals, sometimes there is no fourth wall at all, as in urinal stalls. All the stalls that I can think of are pretty spare and modest, but if you found a fancy stall, you could still call it a stall, maybe a "fancy stall". Most stalls are placed in rows, but as ColleenV pointed out in a comment, often there is only a single shower stall—but public shower stalls are usually arranged in rows.
The etymology of stand is more obvious: it's just a modest, free-standing structure that serves some limited purpose. There's no analogy with stalls for animals. So, there's not even a loose expectation that stands should occur in rows (though they can), or that they should have little more than three walls (though many do), or even that people stand inside them while using them (though many are like that).
On the left is a typical a hot-dog stand in New York. It has no walls at all! In fact, it has wheels so the owner can move it around easily. On the right is a hot-dog stand that has stood for 73 years. It's large enough for a lot more than one or two people, and it probably has more than one room. Take a look at pictures of newsstands and bandstands for some other typical kinds of structures evoked by stand in this sense. And don't miss the picture of a lemonade stand in Peter's answer: that's another very typical, well-known kind of stand—sometimes consisting of nothing more than a table placed outdoors.
As you can see from the examples, neither stall nor stand implies temporariness or permanence.
The difference between stand and stall is not about permanence but grouping
stand - a particular place or location
not to be confused with
kiosk - an enclosed, stand alone structure, usually with a window or opening
toilet / bathroom stall