This is not a good topic per-say to discuss here since it’s such a broad and slightly subjective matter, plus it’s easy to find answers on google.
Responsive design is much more than using percentages. To sum up the difference, it’s optimizing the display of information for all browser widths, something not possible with percentages alone. For example when the display is narrow, the information can be displayed in one format (e.g. horizontal rows) and when the browser is wider it will display the information in another format thanks to the media queries and/or javascript.
Here are some tutorials:
solved Does a website becomes Responsive by using percentages? [duplicate]