I've compared it to plain vanilla copying, and it is indeed faster.

As far as the how, this is what it says on the site: TeraCopy uses dynamically adjusted buffers to reduce seek times. Asynchronous copy speeds up file transfer between two physical hard drives.
I understand the words, but it's still black box to me.

Other features:
# Pause and resume file transfers. Pause copy process at any time to free up system resources and continue with a single click.
# Error recovery. In case of copy error, TeraCopy will try several times and in the worse case just skips the file, not terminating the entire transfer.
# Interactive file list. TeraCopy shows failed file transfers and lets you fix the problem and recopy only problem files.
# Shell integration. TeraCopy can completely replace Explorer copy and move functions, allowing you work with files as usual.
# Full Unicode support.
The pause and resume, error recovery, and interactive file list are very useful too...