Complex sentence: The word "Lesser" in the title shows that the LGPL does not guarantee the end user's complete freedom in the use of software: it only guarantees the freedom of modification for the LGPL-parts, but not for any proprietary software-parts.
Split into simpler sentences: The word "Lesser" in the title of the license is used to show that the LGPL cannot guarantee end user's complete freedom in the use of software. It only guarantees the freedom of modification for the LGPL-parts, but not for any proprietary software-parts.