"Studying" in Brainscape (as opposed to just "browsing") means "using Brainscape's adaptive flashcard repetition process". You will be taken through flashcards and will be asked to rate your confidence in each card, which helps power the Confidence-Based Repetition system and is proven to help you learn faster.
On the website, you can launch a study session by clicking the Study button on any Deck.
In the mobile app, you can launch a study session by tapping on a Deck and choosing the Study option in the menu. In the iOS app, you can even choose a Random Mix across all Decks in your Class, by choosing that option at the bottom of your Class screen.
We hope to improve Random Mix and Custom Playlist features on the website and Android app in the medium-term future.