Sperm cells and egg cells are, respectively, male and female reproductive cells. When they combine inside a woman's reproductive system, they begin gestating and eventually result in a baby. There are a wide variety of differences between these two kinds of cells, ranging from where they come from, what information they carry and how they function. Indeed, the only real similarity between them is that they rely on one another to create a life.
The raw materials for egg cells are formed when girls are still in utero. Every little girl is born with roughly 4 million eggs already in her system, which drop into her uterus once a month or so once she reaches sexual maturity. Sperm cells, on the other hand, are constantly being formed, dying (or being used), then being replaced, in a process that takes around three weeks.
Both sperm and egg cells are produced through meiosis. However, when a sperm cell finishes its second cycle, it is complete, meaning it cannot develop any more. Eggs, on the other hand, finish their development with the first meiosis cycle. When they drop into the uterus, they are halfway between the first and second cycle; the cycle doesn't complete until a sperm fertilizes it.
One of the key hormones used to create sperm is testosterone, while eggs have more estrogen. Both of these are key to the fetus's development, and both provide different secondary sexual features, such as deeper voices and wider hips, respectively. So, a female child will receive her female traits from the estrogen provided by the egg that created her while a male child will receive his male traits from the testosterone provided by the sperm.
While it is obvious to say that sperm develop in men and eggs develop in women, it is important to look the specifics of this process. When sperm develop, they move through the epididymis, which is a tightly-coiled tube in the testicles. As they do so, they are covered in a nutrient-rich fluid that helps them grow. Eggs, on the other hand, develop in a woman's ovaries and are stored in their first phase of meiosis until they are released into the fallopian tube for fertilization.