cpuid[.]com/softwares/hwmonitor.html
Most PCs, laptops, & the graphics cards in many PCs monitor temperatures and adjust cooling fan speeds accordingly. Running fans at lower than max speeds means less fan noise, but it also draws in [sometimes MUCH] less dust, which can eventually clog things up, leading to higher temps. Heat shortens component life spans -- if things get too hot often the device will start throttling CPU speeds downward, trying to prevent more serious damage. You don't have to run software like HWMonitor continuously, but it can be very useful to get an idea of the normal temperature range of the CPU & other critical components, and any reported fans speeds, so that you can spot when something goes amiss. Fan speeds should increase as temps rise, decrease when they fall, and the CPU [& GPU] temps should stay within the normal range for that particular device.
Unfortunately, lots can go wrong...
The BIOS settings may or may not include settings for fans, along with temperature curves that determine fan speeds as set, target temperatures. Importantly, since the BIOS controls fan speeds, a bad version of the BIOS firmware may break that control, so it's something to check & maybe keep an eye on after flashing a new BIOS version.
Be careful if you replace any of the fans, or are selecting fans for a system you're building. The cooling fans themselves can have 3 or 4 wires -- the speed of a 3 wire fan is controlled using voltage, while a 4 wire fan uses something called PWM [ wikipedia[.]org/wiki/Pulse-width_modulation ]. A given BIOS may not be able to work with 3 wire fans, And, not every 4 wire fan is compatible with the fan controller in every BIOS. Some motherboard manufacturers provide optional Windows software for controlling fans -- I've seen many reports where that software worked when setting fan curves etc. in the BIOS did not.
Research any fan before buying -- they've become relatively expensive, making it tempting to shop based solely on price, but it may not be worth it if you have to yank the new fans out & replace them with a more expensive brand/model anyway. The range of fan speeds varies, as does the amount of noise they produce, and the amount of airflow. Liquid or water cooling has become popular -- the fans attached to the radiator are designed for a higher static pressure, which is another spec you'll see advertised.
[When it comes to researching fans, it may be a PITA, but include stuff like reading all the questions & answers on the Amazon product page, e.g., that's the ONLY place where you could find out that a particular model of a certain brand would not work with the standard screws used to fasten every PC case fan since ... PCs really (!).]
PC fans connect to special plugs on the motherboard. There are extension cables if the wires from the fan won't reach, and there are Y cables &/or hubs if you want to use more fans than there are connectors on the motherboard. There are also a couple of brands of controllers that take over the job from the BIOS. All of those may or may not have compatibility problems. There are also manual fan controllers that vary the fan speed as you turn a knob.
On HWMonitor itself, a small, free, & portable version is available. Depending on the CPU & motherboard there are alternative apps, e.g. HWiNFO that *may* be more accurate, but HWMonitor is likely the easiest to use & read, and probably a good choice since you're mainly concerned with what are the normal readings for a particular device, so you can spot when something goes wrong.