I think they mean tricks things like reversing samples, or having a segment of an audio sample keep looping after starting playback so you could "stretch" it longer. Also pitch-shifting samples so you can play them at different notes.
Trackers were strange kinds of sequencers that were very focused on using samples to make music, and they were created at a time when memory was expensive, so you'd typically have fairly low resolution samples (8-bit 22KHz?), and people tried to use those samples creatively because you might not have many of them, both because of memory and hard drive space, but also because they weren't as easy to get as they are today. Most people didn't have the internet at home before the mid-late 90s, and even when people started to have the internet at home, it wasn't like today, the music making community was smaller.
I first discovered trackers in a French gaming magazine around 1997 or 1998, but they had already been around much longer. Said magazine had came with a CD that contained multiple different tracker programs and a collection of music files in different formats (MOD, XM, etc). The compelling thing was that these files were small, because they contained a few audio samples and the data on how and when to play them, so you could fit a tune that was multiple minutes in 1 megabyte or less.
Likewise apparently DJ Shadow pulled off quite a feat with his Akai MPC60 on ‘Endtroducing’, because the sampler could store something like twelve samples, also not too long.
A sorta related anecdote is how the British ‘mind the gap’ was this terse because it was recorded on a solid-state memory, costing dearly in '68 even for the small amount by today's standards.
Trackers allow note data to be annotated with various "effects", triggered via special codes. Some of these effects are things like pitch bends and filter adjustments, which can easily be done in any sequencer. However, effects like retriggering the current sample from an arbitrary offset or rapidly alternating notes in an arpeggio are fairly unique to the tracker workflow. It's not that you can't make those sounds in a conventional DAW, it's just that you probably wouldn't in practice.
