Trondheim Sentral (Trondheim)

For a city the size of Trondheim it's main station is comparatively compact because aside from local trains, it typically only has to handle up to six long-distance trains per day.
So prior to the departure of those trains and particularly after their arrival, Trondheim Sentral can seem crowded.
The main access between the station hall and spor (tracks/platforms) 2 - 5 is by a passage way under the tracks and it can be accessed only by stairs and elevators (hiss).
Hence when a long-distance train arrives, queues can inevitably build up for these elevators, there are no escalators in the station.

The luggage lockers are in this passage way between the tracks and the station hall.

Trondheim Sentral is located on an island on which the city's dockland area is located, but is conveniently located for the city centre, the northern edge of central Trondheim is just across the bridge which is opposite the station's exit.

The former docks area to the north of the station is being redeveloped, so to improve access to and from it a new bridge has been built across the station.
So if you will be heading to/from this docklands area, you can use the elevators on each spor (track / platform) to access this bridge.
The Hurtigruten boat terminal is unsurprisingly in this docklands area, around a 15 - 20 minute wall from the rail station.

Phil Richards from London and downloaded from Wikicommons.

Trondheim airport, which is also known as Trondheim Værnes airport, is 19km from the centre of the city it serves.
Hence the trains to/from Trondheim S station, being the fastest option for an airport to city centre transfer, as the journey time is 34 - 37 minutes.
On some timetables the station at the airport is named Værnes (Trondheim Lufthavn).

Most of the trains which serve the airport are services on the local rail system in Trondheim, which is known as the Trøndelag Commuter Rail.
The trains are operated by SJ NORD but you won't save by booking online; note that the airport website states that the trains are operated by Vy, but SJ NORD has since taken over.

The Trøndelag trains to the airport from Trondheim S will be heading to Steinkjer, though in most hours there is only one departure, so it's a good idea to look up the times in advance on the SJ NORD website.
In addition to the city's main station, Trondheim S, these Trøndelag trains also call at two other stations close to the city centre, Lademoen and Skansen.