Learn Russian: Страница белая.

In Russian, the verb "to be" is almost always skipped in the present tense. Because of this, Страница белая literally translates to "Page white," but it is understood as "The page is white."

Why does the adjective белая end in -ая?

Adjectives have to match the gender of the noun they describe. Страница is a feminine noun because it ends in -а, so the adjective takes the feminine singular ending -ая. If we were describing a masculine noun, the dictionary form would be белый.

How would I use this lesson's question words to ask "What kind of page is it?"

To ask "what kind" or "which" about a feminine noun like страница, you must use the feminine form of какой, which is какая. You would ask Какая это страница? (What kind of page is this?) to get this sentence as an answer.

How do I know it translates to "The page" instead of "A page"?

Russian does not have articles like "a" or "the". You figure out which English word to use based on the context. Since we are stating a specific fact about a page's color here, "The page" is the most natural translation into English.