生 is a picture of a young plant sprouting up out of the ground — the horizontal line is the earth, the rest is the new shoot pushing through. From that single image grew its whole web of meanings: to grow, to be born, life, raw/fresh.
生 is everywhere because life is everywhere: 生日 (birthday, 'life-day'), 学生 (student, 'one who grows in learning' — pairs with 学, which you know), 医生 (doctor, 'master of life'), 先生 (mister/sir/husband, 'born first'), 生活 (life/living). It also means 'raw': 生肉 is raw meat. Few characters open as many doors.
A young plant pushing up through the soil — LIFE, BIRTH, growth.
生 builds a huge family: 学生 (student), 生日 (birthday), 医生 (doctor), 先生 (mister), 生活 (life). It even means 'raw' — 生肉 is raw meat. One sprout, a whole vocabulary.