Learn Russian: Это новая галерея.

When you use это to mean "this is" or "it is" to introduce something, it stays in this neutral, fixed form regardless of the gender of the noun. You only change the gender if you are saying "this gallery" (эта галерея) instead of "this is a gallery".

Where are the words for "is" and "a" in this sentence?

Russian doesn't use a verb for "is" (the "to be" verb) in the present tense—you just place the subject and what it is side by side. Additionally, Russian doesn't have articles like "a", "an", or "the".

Why does the word for "new" (новая) end in -ая?

In Russian, describing words (adjectives) must match the gender of the noun they describe. The noun галерея ends in -я, which makes it feminine. The standard ending for feminine adjectives is -ая, making the base word become новая.

What is the difference between Это новая галерея and Эта галерея новая?

Это новая галерея translates to "This is a new gallery." But if you change the word order to Эта галерея новая, it means "This gallery is new." In the second sentence, the word for "this" attaches directly to the feminine noun, so it must change to its feminine form, эта.