The new feature lets users save content to a Google Feed that you can access whenever.

An APK teardown performed by 9to5Google details a new feature coming to Google Assistant. This feature is named Memory and lets you save whatever content you like to a dedicated feed that can be viewed later. Google describes it as easy, quick way to save and find everything in one place. The feature was enabled from a build that contained some of the features assets.
Memory will be able to save things using a verbal Assistant command and it will be smart about what it saves based on contextual cues. Memory can save: articles, books, contacts, events, flights, hotels, images, movies, music, notes, photos, places, playlists, products, recipes, reminders, restaurants, screenshots, shipments, TV shows, videos, and websites.
A new Memory feed will be added alongside with the current Snapshot feed. This feed will show Today and Older memories as card entries. There will be cards specific for Google Docs, Sheets, Slides, Forms, Sites, Jamboard, and Drive files. The cards will show relevant actions for things that you save. For example, if you save a recipe it may show a Cooking time action or a Track shipment button for a recently placed order.
Source: 9to5Google
Google Assistant reminders will be saved to Assistant Memory. Youll be able to search Memory, and tap on categories like Important or Read later. The screenshots show the new Assistant Memory interface to have only three buttons on the bottom row: Snapshot, Assistant voice command, and Memory. The Google app currently has a Collections tab that may be replaced by Memory.
Source: 9to5Google
In its current state, Google is internally testing this feature with its employees, so its not yet been announced or publicly acknowledged by Google. Theres no sure rollout date for the feature, should it ever become available to all Google Assistant users.