Top sources

Where visitors come from: other websites (referrers), search engines, campaigns and direct visits.

Where

Dashboard → Sources (Top sources). Click a source to filter the rest of the view.

Reading the list

Direct covers typed-in URLs, bookmarks, and visits from browsers or apps that don't pass on where the visitor came from.
Campaigns show up when your links carry UTM parameters such as utm_source. Some campaign reports on Growth and higher build on this.
Clicks on outbound links and file downloads are counted as separate events (and can be goals) — they are not sources.