I presume that every know the difference between wordpress.com and .org websites. Actually in wordpress.com you are not given the option to access your source code and the plugins, there are some default plugins are active by default and works on the cloud.So the wordpress.com blogs are lighter and has less load time.But this kind of advantage is not given to the wordpress.org i.e. self hosted wordpress users .Since you need to install each and every plugin which makes your load time to increase a lot which further affects your seo since search engines also consider your load times while ranking your site.
Now you might have understood the reason for high load times of your blog.Since this is not only your problem and many self hosted wordpress users are having the same.So Automattic launched the Jetpack plugin which that connects to WordPress.com and enables awesome features, powered by the cloud infrastructure.Jetpack is not just a not a plugin with just one or two functionalities.we can say it as a collection of many wordpress.com plugins like WordPress.com Stats,Gravatar Hovercards,Twitter Widget,Shortcodes,Shortlinks,
If you don’t know about these plugins first let me explain about them in brief.
WordPress.com stats – This plugin counts each and every hit of your website and provides you a detailed report about your traffic.A must have plugin for any blog.
Gravatar Hovercards – This helps to know who comments on your blog by providing enhanced information about them like their gravatar,bio and profiles.
Twitter widget – you can keep your readers more up to date by syncing your tweets to your site.
Shortcodes – It decreases your effort by making just a single line code to add images,videos to your site.
Shortlinks – It automatically creates an easy to share mini-url for any post on your site.
Sharedaddy – I guess you may be using different plugins for using share buttons of different websites but this feature brings you all those features making your users easy to share.
After the deadline – Your writing will improve thanks to this artificial intelligence based spell, style, and grammar checker.
Latex – helps you in writing complex mathematical equations in your blog.
And even they are working to add many other features to jetpack.Hope they do it soon.
To use this plugin you must be a wordpress 3.0.5 or a later version user.For some hosts the hosting provider will auto install jetpack.After installing you should use your wordpress.com account to connect to cloud and enjoy all the above features.Finally after knowing all these things you will feel happy to know that this plugin is free and any wordpress.org user can download and install and use it.
And even they guarantee that they take care of every settings while upgrading your already existing plugins with jetpack features.And after installing this plugin you can remove those previously installed plugins.