"It is a plate."
Translation:Is pláta é.
That's exactly right. Irish, like French, has masculine and feminine nouns, but no nouns that are neuter ("it").
There are some endings that indicate whether the noun is masculine of feminine, but it really helps to learn, not just pláta but an pláta because the article an causes the first consonant of a feminine nouns to lenite, if possible. Páirc, which is feminine, becomes an pháirc, but gort, which is masculine, stays an gort.
Look at some of the other answers on this page.
If you are joining two nouns or a noun and a pronoun, you must use the copula. John (noun) is my brother (noun). I (pronoun) am a lawyer (noun). Pizza (noun) is my favorite food (noun) In all of these sentences, you are basically saying that one person or thing is the same as another person or thing. You could use an 'equals' sign to say the same thing, like John = brother
If, on the other hand, you are joining a noun or pronoun to an adjective or a prepositional phrase, you must use a form of bí (like (tá): The plate (noun) is blue (adjective). The dog (noun) is in the kitchen (prepositional phrase) I (pronoun) am tall (adjective). You are not saying I = tall; you're just describing something or saying where it is.