Learn Spanish (Spain): Tú pon la mesa; mientras tanto, yo termino la cena. - You set the table; meanwhile, I'll finish dinner.

Subject pronouns are usually dropped in Spanish. Here, they are included for contrast and emphasis. The speaker is clearly dividing the chores: Tú (you) do this task, while yo (I) do that one.

Is "pon" an irregular command?

Yes, pon is the affirmative informal command (imperative) form of the verb poner. It is one of the short irregular commands. Notice that if you were telling someone not to set the table, you would use the subjunctive mood: no pongas la mesa.

What is the difference between "mientras" and "mientras tanto"?

Mientras just means "while" and connects directly to the action happening at the same time (like mientras termino la cena). Mientras tanto translates to "meanwhile" or "in the meantime." It acts as a standalone phrase, which is why it is followed by a comma here.

The English translation says "I'll finish", so why does the Spanish use the present tense "termino" instead of the future tense?

Native Spanish speakers frequently use the present tense to talk about the immediate future, especially when stating an intention, offering to do something right now, or organizing immediate plans. Saying termino sounds much more natural and immediate here than the future tense terminaré.