A compressed or "Lite" ISO is a modified version of the original operating system where non-essential components have been removed to save space.
Use a tool like Rufus to burn the ISO onto a USB drive (at least 4GB or 8GB is recommended).
The download file is approximately 900MB , making it much faster to download on slow connections.
While convenient, using third-party modified ISOs carries significant risks: Windows 7 Highly Compressed Official ISO (Just 700MB)
Most 900MB files are archived. Use 7-Zip or WinRAR to extract the ISO.
These builds are optimized to run on as little as 512MB to 1GB of RAM . How to Install a Compressed ISO