A turntable's overall sound quality depends on several separate components working together — and the cheapest, most overlooked one (the cartridge) often has an outsized effect on how a whole setup actually sounds.
The cartridge and stylus do most of the actual work
The cartridge (holding the stylus, or "needle") is what physically reads the grooves in a record and converts that into an electrical signal — it has a bigger direct effect on sound quality than almost any other single component in a budget-to-midrange setup. Many entry-level turntables ship with a basic included cartridge that can be upgraded independently later, often for a meaningful sound quality improvement at a relatively modest cost compared to buying an entirely new turntable.
You need a phono preamp — built-in or separate
A turntable's output signal is much weaker and shaped differently than a standard audio line-level signal (from a CD player or phone, for instance), and needs a phono preamp to boost and correct it before it can be played through a standard amplifier or speakers. Some turntables have a phono preamp built in; others require a separate external one, or an amplifier/receiver with a dedicated phono input that includes this preamp function. Plugging a turntable without this stage directly into a standard amplifier input produces very quiet, poorly balanced sound — a genuinely common beginner setup mistake, not a defect in the turntable.
Belt-drive vs. direct-drive
Belt-drive turntables use a rubber belt to turn the platter, which isolates the platter somewhat from motor vibration, generally favored for pure listening. Direct-drive turntables have the motor directly driving the platter, offering more consistent speed and the ability to start and stop quickly and reach full speed almost instantly — traditionally preferred by DJs for that responsiveness, though modern belt-drive turntables have improved enough that the practical difference for casual listening is smaller than it once was.
Record care affects both sound and stylus life
Dust and debris on a record's surface don't just cause audible pops and crackle — they can also accelerate stylus wear over time, since the stylus is physically dragging through whatever's in the groove. A basic record brush used before each play, along with reasonably careful storage (upright, out of direct sunlight and extreme temperature), meaningfully extends both record and stylus life without requiring elaborate cleaning equipment.
The one thing people forget
Check and set proper tracking force (how much downward pressure the tonearm applies to the record) according to the cartridge manufacturer's specification, rather than leaving it at a default or arbitrary setting. Too little tracking force can cause the stylus to skip or mistrack in loud passages; too much accelerates record and stylus wear — this is a real, checkable setting, not just a minor technical detail to ignore.