Event
Event is a type of hit used to track user interactions with content. Examples of user interactions commonly tracked with Events include downloads, mobile ad clicks, gadgets, Flash elements, AJAX embedded elements, and video plays.
Goal
A configuration setting that allows you to track the valuable actions, or conversions, that happen on your site or mobile app.
Goals allow you to measure how well your site or app fulfills your target objectives. You can set up individual Goals to track discrete actions, like transactions with a minimum purchase amount or the amount of time spent on a screen. Each time a user completes a Goal, a conversion is logged in your Analytics account.
Conversion
A completed activity, online or offline, that is important to the success of your business. Examples include a completed sign-up for your email newsletter (a Goal conversion) and a purchase (a transaction, sometimes called an Ecommerce conversion).
A conversion can be a macro conversion or a micro conversion. A macro conversion is typically a completed purchase transaction. In contrast, a micro conversion is a completed activity, such as an email signup, that indicates that the user is moving towards a macro conversion.