As an example, you would have a lead source of PPC and then several campaigns attached to it for PPC - 2016, PPC - 2017, PPC - 2018. This way, when you report, you can look at the high level of how your PPC efforts have performed and then how the individual efforts faired.
To create or edit lead sources:
1. From the menu, click Settings --> Sales & Marketing Settings.
2. Go to the section Lead Management and click "Lead Sources."
3. Click the Add Lead Source button.
4. Enter a Lead Source Code and a Name for your lead source. Then, click OK.