There are an infinite number of things we could consider "large files". But within the context of web development, the most common types of large files are probably:
A mime type is just a web-friendly way to describe format of a file. It's kind of like a file extension, but more standardized and built for the web.
Mime types have a type and a subtype, separated by a /. For example:
image/pngvideo/mp4audio/mp3text/htmlWhen a browser uploads a file via a multipart form, it sends the file's mime type in the Content-Type header.
Up until now we've allowed any file type to be uploaded as a thumbnail... let's fix that.
When you're done, answer the question.