Web services are smart websites that don't just share information, but help you get work done. They may let you store information, give you the functionality of programs installed on your computer, let you communicate with friends, or allow you to collaborate with others. You always get to use the latest version without having to install anything on your computer.
On the other hand, they may lack some of the features you need, or work a little slower than you would like.
It is a balancing act between power and convenience, between working alone and working as a team, between having your information on one computer, and being able to access it from any computer.
Where you fit in the spectrum is the subject of personal preference and practical experimentation. And hopefully the information on this website will make your journey smoother.