Early Twitters remember the “Favorite” button. Twitter users would usually “favorite” something to read later. Twitter later replaced that “favorite” button with the “Like” button.

But today, Twitter is sort of bringing back the “Favorite” button. Twitter is globally launching its Bookmarks feature today. With the bookmark feature, users can save tweets they like that they want to visit later. It’s more like an official “favorite” button. When a user uses the bookmark button, the user of the original tweet won’t know it’s been bookmarked.
The bookmark icon will be where the DM icon was.
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Twitter has said that Bookmarks or some sort of “save it later” feature has been a top request among users.
Bookmarks are rolling out today across Twitter for Android and iOS, Twitter Lite, and the mobile Twitter website.
Source: TheVerge