You’re trying to register your trademark and the USPTO asks you for a specimen. No, you’re not suddenly a microbiologist or an avian taxidermist. Instead, you’ve just run afoul of the USPTO’s jargon. (Yes, that is a terrible pun; and no I am not apologizing for it.)
A mark owner applying to register a mark with the USPTO has to supply a “specimen”–or, simply, an example–of the mark being used in commerce. See Trademark Glossary 1: Use in commerce for why. In the case of a word mark, this can be as simple as a screen shot of your functioning website offering services on the worldwide web. The USPTO’s rules for what qualifies as a valid specimen are numerous and perplexing. There’s even a rule for the submission of a specimen for “scent marks”!
An improper, incomplete or insufficient specimen can prevent mark owners from registering their marks. Relying on a trademark attorney can speed your application through this often needlessly confounding part of the trademark registration process.