Learn Hardcore Italian: Il concerto finisce tardi.

Italian generally requires a definite article before a singular, countable noun when referring to a specific or general thing. Il is the masculine singular definite article that matches concerto (a masculine noun).

What is the part of speech of tardi, and why is there no preposition?

Tardi is an adverb of time meaning late. Adverbs in Italian typically do not take prepositions. If you want to say someone is late, you’d use essere in ritardo instead of adding a preposition to tardi.

What does finisce mean and how is it formed?

Finisce is the third person singular present indicative of finire (to finish/end). Finire is an –IRE verb that inserts -isc- before the endings in all persons except noi and voi:
• io finisco
• tu finisci
• lui/lei finisce
• noi finiamo
• voi finite
• loro finiscono

Why is the adverb tardi placed at the end of the sentence?

Italian adverbs of time most commonly follow the verb. The pattern subject + verb + time adverb is the most natural order. Moving tardi elsewhere can sound marked or emphatic.

Could I use the present tense here to talk about the future, e.g., a scheduled event?