A golem is a creature that has been constructed via magic as a servant or protector for the person who created it. The body of a golem is normally constructed from a single raw material, such as rock or clay. Golems are unintelligent, mindless entities and cannot act on their own. They also will not obey anyone other than the person who created them.
Historically, golems originate from Jewish and Medieval folklore, the word "golem" itself meaning amorphous or unformed.
Golems are made by molding the material in the shape the golem is desired to be, most of the time being humanoid, but animal shaped golems aren't unheard of.
After that a ceremony is held to bring the golem to life, which involves writing the Hebrew word, "Emet" or "life" on the forehead.
The golem is no different from an automoton, it mindlessly follows instructions and will continue to do what it's told untill it's told to stop. Each day they grow to be a little bigger and a little stronger.
As they live amongst humans, they yearn for humanity, but know that it'll be no more than a creation of mans, causing anger. If one allows it to get to be too big and strong, it can go on a rampage. The only way to destroy it is to erase the first letter of Emet (since it's in Hebrew, the first letter would be on the right side.) turning it to Met, meaning "death".
Golems have taken on different elemental forms ever since their recurring appearances in various media (video games, movies, etc.). These include fire, nature, and metal.