The 8 track was considered a cartridge. It contained 4 separate bands of right and left channel on a continuous loop wide magnetic tape.
The cassette contained a right and left channel on each side of the narrower tape that reguired reversing to play the second band making it similar to a reel-to-reel design.
Both were designed to hold just a single album so the advantage with the cassette was that it was smaller and more portable. The disadvantage was that you had to eject it and flip it over to play the other side.
The difference in tape cartridge size can be seen here.
View attachment 1715390426
People used to say the 8 track sounded so much better, but that was in the early days before magnetic tape technology and tape player head technology evolved to make the difference nearly zero.
Of course, the advent of CD digital optical recording technology made the magnetic analogue recording and playback technology obsolete very rapidly. Computer technology then quickly advanced so that the optical discs and readers of the CD were no longer required and now it is all on a memory chip.