Countries where Mandarin Chinese is spoken are often strongly influenced by Confucian ideals. Part of the Confucian tradition is a deep respect for teachers.
Lǎoshī is the Mandarin word for “teacher.” It has two characters: and the first character lǎo is a prefix which means “old.” The second character shī means “teacher,” so the literal translation of lǎoshī is “old teacher.”
Lǎoshī is used as a title. You can address your teacher as “lǎoshī” or you can use lǎoshī in combination with a family name when referring to a teacher.