Whats the difference between sperm and semen in men?

Sperm is in semen. Semen or seminal fluid is the whitish viscous fluid emitted from the male reproductive tract that contains sperm & liquids (seminal plasma) that help keep them viable. Sperm cells, produced by the testes in humans, represent 2--5% of semen volume. An average ejaculation of a human male expels 2--5 ml, containing 200--300 million sperm.
Important. Semen contains fluid and sperm. That fluid contains certain chemicals. The sperm is what helps achieve pregnancy and is ultimately the important part. The semen has fluid which transports the sperm.