I’m gathering a collection in which I have people link to their websites. However most of the links (when clicked on) in my website leads to a 404. I tried changing to https:// and that made the links work. Does all the links have to be in that format in order to work? seems kind of unnecessary.
Yes you need to specify a full URL. About 95% of sites on Google begin with https://, but about 5% still use http://. There are a lot of historical reasons for using absolute URLs- today it mostly comes down to distinguishing absolute from relative URLs, and protocol distinctions.
For instance, example.com is a valid relative path, so if you tried to create a link like that on your site;
<a href='example.com'>Go here</a>
Your browser would resolve to something relative on your site, like;
https://www.mysite.com/example.com
Browsers expect an absolute URL when you want to navigate to a different website from the one you’re currently on.