Pros:

• Websites can't see your real IP and thus can't figure out your real location that easily
  • You might also be able to blend in with other users who use the same VPN server
• Your ISP can't see what you're websites you're connecting to
• Your Network operator (e.g. a coffee shop offering public wifi) and you're ISP can't see your unencrypted connections (e.g. HTTP, Telnet)
• You can bypass regional censorship or other forms of content unavailability

Cons:

• Your VPN provider can see everything you're connecting to (but not the content if you use HTTPS, which thankfully has become very common), so you need to be able to trust them
• A good and trustworthy VPN usually costs money
• Slightly slower connection and higher latency

Things to look out for when choosing a VPN provider:

• No-log policy
• Regular security audits
• Open source client applications
• Private/anonymous payment options (crypto currency)
  • Monero is the best option if you want to stay fully anonymous
• Minimal information required for signing up, ideally none (some providers don't even require an email address, they just give you a random generated Account ID)