When you download a large file or an installer, it may have been corrupted in transit or swapped out by someone in the middle. You can verify this by comparing the checksum (a hash value such as SHA-256) published by the source against the hash of the file you received.
The process is simple. Drag the downloaded file onto AG HASH's File tab, and hashes like MD5 and SHA-256 are computed automatically. Paste the expected hash listed on the download page into the Verify box, and the matching algorithm's row is highlighted green.
A green match means the file is identical bit for bit, which means there was no corruption or tampering. If no row matches, on the other hand, it's safer to download it again or use a different mirror.
Whenever possible, verify with the strongest hash the source provides (SHA-256 or better). If only MD5 or SHA-1 is offered, it will catch accidental corruption, but to guard against malicious tampering you'll want a signature or a SHA-256 checksum alongside it to trust the result.