It's the imperative form of the verb "donner" (to give) in the second person plural (you all).
Examples:
* Donnez-moi un café, s'il vous plaît. (Give me a coffee, please.)
* Donnez-moi votre numéro de téléphone. (Give me your phone number.)
* Donnez-moi la main. (Give me your hand.)
It's important to note that in formal situations, you would use the formal "vous" form, which would be "donnez-moi".