This can be an SSD or a mechanical HDD. It is used to store all data, including the OS, games, documents, and apps.

An SSD is generally faster than an HDD, as it can process, read, and write data faster. Mostly gamers and casual workers use SSDs for storage.

An HDD is a slower method of storage used everywhere in the last 30 or so years. Nowadays, HDDs are used for servers and computers with large storage requirements.