Rails is a web application development framework written in the Ruby language. It is designed to make programming web applications easier by making assumptions about what every developer needs to get started.
It allows the user to write less code while accomplishing more than many other languages and frameworks. Experienced Rails developers also report that it makes web application development more fun. Rails is opinionated software. It makes the assumption that there is a "best" way to do things, and it's designed to encourage that way - and in some cases to discourage alternatives.
If the user learns "The Rails Way" they will probably discover a tremendous increase in productivity. If they persist in bringing old habits from other languages to their Rails development, and trying to use patterns they learned elsewhere, they may have a less happy experience.
The Rails philosophy includes two major guiding principles. The first one is the do-not-repeat-yourself that is a software development principle, which states, "Every piece of knowledge must have a single, unambiguous, authoritative representation within a system." By not writing the same information over and over again, the code is more maintainable, more extensible, and less buggy.
The second one is Convention over Configuration, which consists on giving by default the set of conventions Rail considers the best, rather than requiring endless configuration files. Finally, Rails simplifies the user work by the MVC methodology and simple coding, and boosts their development as programmers it gives them the power to change core classes and methods.