Shareware is also often called "User Supported" or "Try Before You Buy" software.

Shareware is not a kind of software, it's a way of marketing software.

The user is permitted to try the software on their own computer system (generally for a limited period of time) without any cost or obligation. Payment is required if the user has found the software to be useful or if the user wishes to continue using the software beyond the evaluation (trial) period. Payment of the registration fee to the author will provide the user with a license to continue using the software.

The RAR (and its Windows version - WinRAR) archiver is shareware.
This means:

• All copyrights to RAR and WinRAR are exclusively owned by the author
  - Alexander Roshal.
• Anyone may use this software for a test period of 40 days.
  Following this test period of 40 days or less, if you wish to continue to use WinRAR, you MUST register.