What’s the difference between a lead and a contact and why do they need to be matched?
A Lead is a prospective customer from an account around whom traditional volume Marketing and Sales are based. A salesperson may pursue a relationship with each lead in order to work towards a Closed Win.
A Contact represents one attribute of an account, so that, in Account-Based Marketing, Marketing and Sales can see this person in the context of the bigger picture of the entire account.
Salesforce keeps track of your Leads, so, in order to be Account-Based, Demandbase integrates with Salesforce to convert the Lead to a Contact for a target account. You can then analyze and take action on your Contacts in the context of Account Based Marketing/Experience.
What does Demandbase match?
Once an account list is created, Demandbase starts performing lead to account (L2A) matching, continually driving your account based analytics, orchestration, and actioning capabilities.
Demandbase automatically matches lead to accounts and populates the custom Matched Accounts fields in Salesforce. You can also manually convert your Lead records to Contact records associated with the Matched Account. See Set Up Lead to Account Matching.
Generate a report on the effectiveness of the system’s lead to account matching with the Lead Matching Report at 
Settings > Lead Matching > Lead Matching Report.
When does Demandbase match leads to accounts?
By default, Demandbase syncs Leads every 5 minutes. You can adjust this setting at Settings >Demandbase-Wide Settings > Data Sync Settings. (See Data Sync Settings.) After leads are synced from Salesforce, it can take 10-30 minutes to be matched in Demandbase One, depending on the volume of changes with leads. When matching occurs, Demandbase updates the Matched Account field on the Lead. (See, for example, 
Database > Analytics > Fields).
How exactly does matching work?
Demandbase considers the company name and email when matching a lead to an account.
In addition, we use geographic fields (country, state/region, city, postal code) to differentiate multiple equally good matches based on company name and email. The system compares the company name on the lead with the account name, performing fuzzy matching to normalize variations in how names are entered. For example, Demandbase recognizes that Microsoft Corporation, Inc. and Microsoft are the same company. For email addresses, the system compares the email domain on the lead with the company website from the account.
The prioritization / differentiating rules when there are multiple matches work as follows:
- When there's both a company name match, AND an e-mail match to the same account, that match has the highest priority.
- A company name match alone (without an email match) has second priority.
- An email match (without a company name match) has third priority.
If there are multiple accounts that match to a given lead with the same priority, then one is selected based on the best geographic match. The quality of a geographic match depends on how far down the geographic hierarchy a match exists: Country < State/Region < City < Postal Code. When performing a geographic match, the system understands that different spellings resolve to the same country or state (example: United Kingdom vs. the UK).
When matching occurs, Demandbase updates the Matched Account field on the the Lead with the mapped account.
Why isn't a specific lead matched?
For the system to run the lead to account matching:
- The account needs to belong to an account list.
- The user syncing Demandbase and Salesforce together must have access (visibility) to that lead.
- To convert to a contact, the lead cannot be a queue. It must have an explicit owner.