What is the difference between employer brand and employer branding?

Employer brand is the noun, the asset, your standing reputation as an employer. Employer branding is the verb, the deliberate activity you undertake to research, define, communicate and improve that reputation. One is the result; the other is the work. The distinction matters because you can invest heavily in branding activity, such as campaigns, content and events, and still have a weak brand if the underlying experience does not back it up. Conversely, a genuinely great workplace can have an under-managed brand simply because nobody tells the story. The pitfall is confusing activity with outcome: shipping more content is not the same as changing how people perceive and choose you.