jQuery has been evolving since day one. There are two major releases available for download. The versions 1.x and 2.x differ in a way; 1.x is more stable and supports older browsers as well; whereas, 2.x has the same API as 1.x but without the support for legacy browsers.
Note
A legacy browser is an older version of a browser that has not been updated to the latest available version.
If you are using jQuery for a project, you can get another version that takes fewer resources and is faster to load.