The free-text search on your newsfeed allows you to filter your stories by setting your search keyword as the keyword filter.
Once you enter your search keyword in the Search Bar (at the top of your Newsfeed), it will show up as a tabbed bar on the top of your newsfeed.
You can save your searches, or reset them with the reset button. Once you save a search, you have to specify the Section title. The filter will be pre-set as the keyword you searched for.
You can also create an email alert from your saved search from the save menu. The email alert will be sent on the selected days at the chosen times. You can also customize your template, select days and the time you want the alert to be sent on, and have the alerts grouped by the available smart filters.
You can find all your saved searches by going to the user menu and clicking on saved searches.