It really depends on who you ask.
VPNs were originally intended to use for accessing information inside a network without exposing more than necessary of the network.
However, commercial VPNs mostly just hide your IP-address and sometimes change the path your internet traffic takes.
This is useful if your ISP sucks at peering to some specific places (Like mine: traffic going from me to eastern Europe takes a route that adds about 80ms ping compared if I just connect to a VPN server in Poland) and if you want to download some files without anyone knowing it’s specifically you that downloads them.
There are also cases where certain websites are blocked by your country, and you still want to access them. For example, maybe you want to use Instagram in China, but china says no. Then you can use a VPN to route Instagram via another country so China doesn’t know that you’re sending reels to your friends. (Unless China says no to the VPN too).
Masking your IP-address could also be useful to avoid network attacks (primarily DDoS) from games that expose your IP, such as GTA 5 Online, but those games are rare, and getting attacks are even rare-er, but having that extra protection is good if you’re a popular streamer.
Yet another pro of the encryption most VPNs apply is that your ISP can’t see any of your traffic, just some metadata and which VPN server you’re using, but this isn’t a problem in any western country for regular users, and HTTPS has already got your back anyway.
Most people don’t need a VPN, and companies like NordVPN has taken the marketing too far. A VPN won’t protect you from hackers stealing your bank account or improve your speed. 80+ procent of internet users don’t need a VPN, and your favorite YouTuber most likely doesn’t know what they’re talking about (unless it’s someone like Linus Tech Tips, which actually is pretty transparent about it).
Of course there are exceptions to this, but they are very rare.
Sometimes changing IP can trick some websites though, so it’s become very popular to use for accessing other Netflix, Hulu, primevideo, etc catalogs which might differ from your home country. A popular example is Japanese Netflix which has a lot more anime compared to American Netflix.
TLDR:
A VPN is (sometimes) good if you want to watch foreign Netflix, or if the guys that supply your internet can’t properly do their job.
If you want to read more about it (which you probably don’t if I’m being real, it can get quite nerdy), I’ll list two sources by VPN providers about what a VPN is. They are biased, but it does give you some extra insight.
mullvad[dot]net/en/vpn/what-is-vpn
azirevpn[dot]com/support/faq (Two top questions, as of February 2025, rest is marketing).