1. Userbase and Audience: One key difference between Quora and Tumblr is their user base and audience. Quora is primarily known as a platform for seeking experts' opinions and knowledge, attracting a more professional and serious user base. In contrast, Tumblr has a younger audience that focuses more on creativity, self-expression, and entertainment.

2. Content Format: Another significant difference is the type of content each platform focuses on. Quora is more text-heavy, featuring long-form questions and answers that are informative and educational. On the other hand, Tumblr is image and multimedia-focused, with users sharing visuals, gifs, videos, and short-form content for entertainment and self-expression.

3. Community Interaction: In terms of community interaction, Quora emphasizes quality discussions and knowledge-sharing through comments and answers. Users often engage in thoughtful debates and offer well-researched responses. In contrast, Tumblr emphasizes reblogs, likes, and comments on posts, creating a more casual and supportive environment for creative expression.

4. Moderation and Policies: Quora has a strict moderation policy in place to ensure the quality and authenticity of content shared on the platform. Misinformation and hate speech are closely monitored and removed. Meanwhile, Tumblr has faced criticism for its lenient moderation policy, leading to issues with inappropriate content, spam, and cyberbullying.

5. Social Networking Features: Quora focuses more on establishing professional connections and networking among users, with features like following specific topics and users, requesting answers from experts, and messaging. In contrast, Tumblr has a more social networking aspect, allowing users to connect through content sharing, reblogging, and likes within a more casual and visually appealing interface.

6. Monetization Opportunities: Quora offers monetization opportunities for content creators through its Partner Program, where writers can earn revenue based on the engagement and views of their content. In contrast, Tumblr does not offer direct monetization options for users, making it more suitable for personal expression rather than income generation.

In Summary, Quora and Tumblr differ in user base and audience, content format, community interaction, moderation policies, social networking features, and monetization opportunities.