In fact all the difference between internal and external sound cards lies in the location of the device. The former are either unsoldered on the motherboard or connected to it via the PCIe interface. The latter are placed on the outside of a computer or notebook (they don’t carry their name for nothing) and are connected via USB.
Here we could finish the story, but there are a couple of very important issues regarding the work of internal and external sound cards that would be good to discuss.
Integrated and discrete sound cards

The first thing worth noting is that there are two types of “internal” audio cards: integrated and discrete. The former are soldered directly onto the motherboard and usually have relatively low performance. They are enough to connect speakers or headphones to your computer – well, so as not to leave it “mute”.
The discrete solutions are a bit more interesting. They are extremely versatile. There are very simple solutions that can be used just to replace a broken or missing built-in audio card, and professional configurations that can handle full 5.1 or 7.1, with special feedback technology or recording of vocals or music.
And, moreover, since discrete add-in cards are connected via PCIe interface, which has a high bandwidth, professional audio producers and musicians prefer them to the “external” ones. Gamers will also like these models. For example, Asus produces special versions of the ROG gaming series, which provide surround sound for deep immersion in the virtual world.
“External doesn’t mean good, internal doesn’t mean bad
As is clear from a couple of paragraphs above, there are both simple and highly professional discrete internal “soundcards”. And why external ones are worse?
There are extremely simple USB sound cards. They are sold by the kilos in online stores, cost mere pennies and offer just audio outputs. That is, if the built-in audio card is broken, you can buy a plug-in USB one for a couple of hundred rubles and use.
Professional external “audio players” also exist. And in some cases they are even more convenient than integrated ones. For example, they may have physical control elements on them through which you can adjust the device operation (buttons, “knobs” and other “wheels”). This will help to quickly adjust the quality of playback or recording.
Professional-grade USB audio cards have a lot of performance requirements. The interface that connects them can’t provide the same bandwidth as PCIe. So “external” sound cards need to encode the signal in such a way that it is of high quality – but small in volume.
Conclusion
Choosing an audio card,You should not be guided by the type of its deployment but by its intended use.If you want to install a speaker at home 5.1 or 7.1 with volumetric audio – both built-in and external will do. To record sound from an electric guitar, which is overloaded every now and then, it is better to use a remote with control elements. And if just an integrated “sound card” is broken, the cheapest one will be enough, regardless of type.
And only when choosing a sound card for a laptop question “Remote or integrated?” does not arise. Only attachable via USB. You just can’t install an embedded one in it.