Widgets are used to manage your sidebar. You have two sidebars- one for the homepage and one for all the other pages.
You manage widgets by going to appearances>widgets and dragging widgets form the left side to the right side.
You have two choices with sidebar widgets. You can put widgets in the sidebar and it will effect all pages or you can use the “page sidebars” widget. Drag it to the sidebar widget area and save changes. Then go to each individual page and there will be a spot to add sidebar content for that particular page. This way you can have unique sidebar content on all pages if you wish.
You will most often use the text widget. This is a blank widget that you can put code into. You can embed a you tube video, pictures, write text, whatever you like.
Here’s a decent tutorial video that explains some widget basics…