Learn Swedish: Mannen kliver in i hallen. - The man steps into the hall.

The combination in i is a compound preposition meaning into. It shows motion from the outside to the inside of a space. If you just used i, it would mean he is already inside the hall and just stepping around.

Could I just say Mannen kliver in hallen without the i?

No, you need the i. in tells us the direction (inward), but i is required to connect that movement to the specific destination (hallen). Together, in i gives us into.

What is the difference between kliver and går?

kliver specifically means to step or take a distinct stride, whereas går is the general word for walk or go. kliver is frequently paired with directional words like in i (into) or ut ur (out of) when someone physically crosses a threshold.

What exactly is hallen in a Swedish context?

While it can mean a large public hall, in a normal home context, en hall is the entryway or foyer right inside the front door. So the man is stepping through the door into the entrance area.