What is goal in Google analytics?

Goals in Google Analytics allow you to track specific user interactions on your site. These user interactions can be anything including form submissions, button clicks, ebook downloads, and more. When a website visitor performs the specific action that you've defined as a goal, Analytics records that as a conversion.

Hi Friends,
Goals As the name suggest is the outcome that you predict From your efforts.
Every site that is into existence have some goal Like some want to sell something, some site want user to stay on their page and read whole article, some site have query forums that they want user to fill and they follow that querry offline.

These are goals that you set in google analytic(Or any analytic softaware) so that you can measure how much fruitful your efforts is ?
Suppose you want to sell Bag on your site, You set that goal in google analytic(put google provided code on your "thank you" page,So that google can came to know that's the required action you want your to follow ) . A user come on your site and purchase the Bag,that's mean you get 1 goal completed on your site.

When a website visitor performs the specific action that you've defined as a goal, Analytics records that as a conversion.

A goal represents a completed activity, called a conversion, that contributes to the success of your business. ... Having properly configured goals allows Analytics to provide you with critical information, such as the number of conversions and the conversion rate for your site or app.

Goals measure how well your site or app fulfills your target objectives. A goal represents a completed activity, called a conversion, that contributes to the success of your business.