Nouns in Spanish are a bit confusing, because they have a gender. That's right, they are either masculine or feminine. Most nouns follow a pretty obvious pattern (-o or -a endings), but it's wise to always memorize the gender when you learn any noun that breaks the pattern. Some nouns end in -e, and some nouns will surprise you because they are exceptions.
Adjectives agree with the noun they modify in number and gender. Except for adjectives that end in "e" (e.g., grande) generally adjectives end in "o" if they are masculine and "a" if they are feminine. Additionally we add an "s" to make them plural. For example:
Marcos es alto. Marcos is tall.
María es alta. María is tall.
Marcos y Juan son altos. Marcos and Juan are tall.