When you 'Contribute' a document, you are publishing it to the Community for everyone to read and use. This will mean that other people on the platform are able to see, comment on, and like your document.
Additionally, depending on if you select "Freebie" on the document you upload, people will also be able to download a watermarked copy of your notes to their device for personal use too! For more information on this, see: Downloading Study Materials.