Both “de løper rundt” and “de løper omkring” are also correct. “De løper rundt” could also mean that they are running around something, such as around the house. “De løper rundt omkring” would mean that they are running around in some particular area without any particular plan or direction, though the two other sentences can also have this meaning. In most situations they are interchangeable.
not exactly. you can think of it like an expression with no literate meaning in english. sometimes you can't find similar expressions in your language and that's fine because it works as a startup to assimilate natural abstract meanings directly from your thoughts to those norwegian idioms and other terms without struggling to remember specific words in your language with inaccurate translation. keep it up even with simple words so you're on your way to fluency!
So rundt is something like encircling and omkring would be used for proximity, while "around" in English just goes both ways. You could gesture to an area saying "it's around here somewhere" and that's omkring but you say "I'm driving around the block to find a parking spot" and that's rundt. Is that right?
In English we have the expression "running round and round" usually followed by "in circles"....but not always....sometimes we get more metaphorical...."like a chicken with it's head cut off"...I don't know if this is the same sentiment implied here in the Norwegian, but I am curious what the difference is if it's not....