Answer
XAML Hot Reload applies markup changes to a running app without rebuilding; .NET Hot Reload applies many C# edits live. They speed up UI iteration greatly. Limitations: some structural code changes, new fields, or signature changes require a full rebuild, and not every edit is supported—expect occasional restarts.
Real-world example A developer tweaks padding and colors in XAML and sees updates instantly on the device, iterating on layout in seconds.