It's not gibberish, it's an `Id`, which is the type of data Salesforce stores for all `Lookup` or `Master Detail` relationships. If you want a linked name, you will need something more like the below. I would change the `var` to `assignment` to be less confusing.

    <apex:outputLink value="{!$Action.User.View, assignment.Team_Member__c}">
        {!assignment.Team_Member__r.Name}
    </apex:outputLink>

SOQL:

    SELECT Team_Member__c, Team_Member__r.Name FROM Team_Assignment