さくらは きれいな はなです / Cherry blossoms are beautiful flowers.

さくら

means "Cherry blossoms".

きれいな

means "beautiful" which is adjective. and it's end with "な", so it called as na-adjective.

はな

means "flower".

きれいな　はな

means "beautiful flower". You can put an adjective just in front of the noun.

さくらは　きれいな　はなです

means "Cherry blossoms are beautiful flowers.". this is "A is B" grammer.

ふじさんは　たかい　やまです。

"ふじさん/Mt.Fuji", "たかい/high, tall", "やま/mountain". In the same way, this means "Mt. Fuji is a tall mountain". 

However, this adjective "たかい" is of another type of adjective. This is called i-adjective, because this is ending with "i". 

There are two types of adjective. One is i-adjective, another is na-adjective. Please keep in mind.