Lead source answers the question: where did this person come from? Common lead source values include organic search, paid search, social media, email marketing, events, referrals, content syndication, partner, outbound sales prospecting, and direct/unknown.
Lead source is typically set once, at the moment of lead creation, and does not change. This distinguishes it from campaign attribution, which tracks all touchpoints throughout the lead lifecycle. Lead source tells you which channel brought someone into your world. Attribution tells you which activities influenced their journey through the funnel.
For MOps teams, lead source governance is an ongoing battle. Without standards, sales reps manually enter values like "website," "the website," "web," and "Website" all referring to the same source. Build a picklist with predefined values and lock it from free-text entry. Map automated lead creation sources (form fills, integrations, imports) to the correct source values programmatically.
The most valuable analysis of lead source data connects source to downstream revenue, not just lead volume. A source that generates 1,000 leads but no pipeline is less valuable than a source that generates 50 leads that close. Build reports that track lead source through the full funnel: leads created, MQLs generated, SQLs accepted, opportunities created, and revenue closed. This is how you justify budget allocation.
Lead source reporting has a known bias toward trackable digital channels. Events, word of mouth, podcasts, and dark social are harder to attribute and often end up in the "direct/unknown" bucket. Acknowledge this limitation in your reporting rather than pretending digital channels are responsible for all pipeline.