Firefox comes with a list of different search engines which can be used directly from the search bar by switching between them through a single click.
So, each of these engines can be used for different types of searches online. To check product prices, Amazon search can be selected, for general information, Wikipedia search can be used and so on.
Switching between these different search engines, adding new ones or removing existing ones can be directly done through a few clicks. Before searching, click on the + icon in the search field at top right in Firefox.
Then from the Search with: section, choose any of the available ones (default list includes the commonly used ones like Google, Bing, Amazon, Wikipedia). To add new search engines or remove the existing ones, click Change Search Settings.
Uncheck those that are to be removed from the list. For adding others, select Add more search engines.
This will list the other search engines available from the Firefox add-ons page.
Smart keywords can also be added for various searches. Happy searching.