Learn Russian: Это яйца, а там бананы. - These are eggs, and over there are bananas.

Яйца (eggs) comes from the singular word яйцо (egg). Because яйцо is a neuter noun ending in -о, its plural form changes the -о to an -а. Notice that the spoken stress also shifts: from яйцо́ to я́йца.

How is the plural formed for бананы?

The singular word is банан (banana). It is a masculine noun ending in a consonant. To make most regular masculine nouns plural, you simply add -ы to the end, making it бананы.

If яйца is plural, why do we use Это instead of a plural word for "These are"?

In Russian, when you are introducing or pointing to things, you always use the fixed word Это, regardless of whether the thing is singular, plural, masculine, feminine, or neuter. So Это can mean "This is" or "These are" depending on what comes next.

Why does the sentence use а instead of и for "and"?

Russian uses а to show a slight contrast. Here, you are contrasting two different things in two different places: "These are eggs, whereas over there are bananas." The word и is used for joining similar ideas without any contrast.