IVF (In Vitro Fertilization) and ICSI (Intracytoplasmic Sperm Injection) are both assisted reproductive technologies used in fertility treatment, but they differ in one crucial aspect. While IVF involves fertilizing an egg with multiple sperm in a laboratory dish, ICSI involves injecting a single sperm directly into an egg, increasing the chance of fertilization in cases of male infertility or low sperm count.