In Spanish, the imperative mood as strictly understood can be used only in the familiar second person (tú and vosotros). However, the term "imperative" is frequently used for commands given in the formal second person (usted and ustedes) as well as the first-person plural (nosotros and nosotras). In those cases, and well as with negative commands, it is technically the subjunctive mood that is being used.
In English, the imperative mood can be made by using a simple unconjugated form of the verb without any subject attached. For example, the complete sentence "Go!" is in the imperative mood; the subject "you" need not be stated.
In Spanish, the tú form of the imperative usually uses the same conjugation as the third-person singular indicative. Thus a verb such as estudia can, depending on the context, mean either "you study" (as a command) or "he/she studies." When a pronoun is used in the Spanish imperative, it typically follows the verb: estudia tú.
The plural (vosotros) form of the imperative is always formed by changing the final r of the infinitive to a d. Thus estudiad means "study" as a command to multiple listeners. The vosotros imperative is very rare in Latin America; the ustedes form of the subjunctive is used instead.
Note that the imperative mood as strictly understood cannot be used in the negative, i.e., with a no. The negative subjunctive must be used instead.