A fake wallet app is one of the oldest ways to steal bitcoin. Serious wallet and node projects publish a SHA-256 hash for every file they release: a 64-character fingerprint that changes completely if a single byte of the file changes. Most guides tell you to compare it on the command line. This does the same comparison in your browser.
Choose the file you downloaded, then paste the published hash, or the whole SHA256SUMS list, and the checker finds the right line by file name. A match proves the file is the one on that list. It does not prove who wrote the list: for that, projects also sign it, and the lesson below walks through checking the signature.
Related lessons: Verify a download before you install it, Scams aimed at holders.