To change any front-end functionality you can change the active theme only. In that case uploading/replacing only the theme (theme folder) will solve the issue.
If you changed any or your plugins, then uploading/replacing only the plugin (plugin folder) will solve the issue.
But if you uploaded an image, added/edited a post/page/media etc. then it's a database change. In that case it's a bit critical:
- If, except the new changes all other things are same in both local and server, then you have to upload only the updates. You have to upload the
/uploads/* folder and have to replace the server database with the recent local one.
- If, you did some changes in your server also, and then you made some local database changes and both the versions are not same, then I'm afraid, it'd be a massacre. You have to update your server database one by one, only with the fresh changes.
That's the brief.
Okay, after your comment:
OKay, what I did was add some text content to another page that was
blank so that means I would have to upload the upload folder and
replace the database. With regards to the database, do I have to
completely delete the database on the server and upload the modified
localhost one? If I did that wouldn't it change all the links again in
the database i.e.: all the links would be the localhost ones again..
Have a look at this WPSE thread.
And no need to upload the whole database, just delete all the tables of your server database, and changing the server path, export and then upload the local tables into server db. :)