Let's jump on the Trim bandwagon!
Trims as explained earlier are used to control the speed of a ride. I will do my best to give an ELI5 for you
Trim brakes are common on roller coasters to make sure the trains do not go too fast through the track. If a train travels through a certain part of track too fast it can be painful for riders.
In the picture you specify that track is made by the roller coaster manufacturer Bolliger & Mabillard (B&M). One of their key focuses on roller coasters is comfort along with fun and safety. To keep all in check they use trims in areas where they need to control the speed more so you will see them on a lot of their mega, hyper, or giga coasters as the train goes very fast throughout the entire ride.
click here for an exampleTrims can be used in many different ways, though the most common is to "trim" a little speed off in as little as 1km/h incriments they can also be used to slow the train way down for a more compact piece of track.
click here for an exampleBottom line trims are used to make the riders more comfortable. Enthusiasts complain because some want more forces. It is all perspective.