A widget is a portable chunk of code that can be installed and executed within any separate HTML based web page by an end user without requiring additional compilation. If you are using "blogger" as your blogging platform, then you may be more familiar with the term "gadget" examples of those are "recent posts", "recent comments", "labels", "newsreel" and "profile" those are some of the basic widgets/gadgets blogger has to offer, however there are other widgets/gadgets on the internet that are also free of use. Most of them require manual installation of the code to your blog. But how do you add a widget/gadget in your blogger blog? Follow this short tutorial and you'll know how.
Login to your blogger account and then you will be in what is called your "dashboard", it contains all your blogs and your account information
Find the blog you want to install a widget into then click > Layout
Once you are in your blog you should see something like this
Locate the area with a "Add a Gadget" labe where you want to put your chosen widget into