Hides ur IP address from the websites you visit and any peer to peer services, which otherwise could be used to geolocate you or identify whoever’s name is on the internet plan. They also block your ISP from seeing what connections you are making, but this is just a shift of trust as the VPN provider will then get that information so you need to trust that they won’t log it or sell it

Your last-mile cable/fiber/wireless ISP is likely a subsidiary of one of the world's largest IP holdings companies, and if they aren't, they likely have big contracts with them and will bend over backwards to please them. They also have a lot of politicians under their thumb, which is necessary to maintain their extortionate regional monopolies. They have a financial incentive and the resources to observe your traffic and send you legal threats or disconnect you unilaterally.

When you use a VPN you are just letting some other company see what your ISP could see (i.e. every website and server you connect to, and how much data is being transfered, if not the plaintext of the data itself). Your ISP can still glean a lot based on the time and amount of data being transferred between you and your VPN, even though it is all encrypted. The VPN has different incentives than a multinational IP conglomerate, but at the end of the day still has to comply with the law. Some of them are legit. Some of them are literally run by Mossad. They generally solve the problem for media piracy, but should not be used thoughtlessly if there is any serious criminal or political risk involved.