The polite or honorific sentence style used to show respect to the addressee; in Japanese typically the 'desu/masu' style.
ビジネスの場では敬体（です・ます調）を使うことが多い。
In business situations people often use the polite (desu/masu) style.
友達同士の会話では敬体より常体の方が自然だ。
In conversations between friends, the plain style (joutai) is more natural than the polite style.
作文は先生に提出するので敬体で書いてください。
Please write the composition in the polite style because you'll submit it to the teacher.