Tlaloc (Tlāloc) is the god of rain in Aztec religion. He was also a deity of earthly fertility and water, worshipped as a giver of life and sustenance. This came to be due to many rituals, and sacrifices that were held in his name. He was feared, but not maliciously, for his power over hail, thunder, lightning, and even rain. He is also associated with caves, springs, and mountains, most specifically the sacred mountain where he was believed to reside. Mount Tlaloc is very important in understanding how rituals surrounding this deity played out. His followers were one of the oldest and most universal in ancient Mexico.
There are many different representations of Tlaloc, and there are many different offerings given to him. Tlaloc is often represented through iconography of butterflies, jaguars, and serpents. The Mexican marigold, Tagetes lucida, known to the Nahua as cempohualxochitl, was another important symbol of the god, and was burned as a ritual incense in native religious ceremonies. Representations of Tlaloc are distinguished by the presence of fangs, whether that be three or four of the same size, or just two, paired with the traditional bifurcated tongue. Often, but not always, Tlaloc will also be carrying some sort of vessel that contains water.
Although the name Tlaloc is specifically Nahuatl, worship of a storm god, associated with mountaintop shrines and with life-giving rain, is as at least as old as Teotihuacan. It was likely adopted from the Maya god Chaac, perhaps ultimately derived from an earlier Olmec precursor. Tlaloc was mainly worshiped at Teotihuacan, while his big rituals were held on Mount Tlaloc. An underground Tlaloc shrine has been found at Teotihuacan which shows many offerings left for this deity.
In Aztec iconography, many different sculptures, and pieces of work have been miss-labelled or mistaken as Tlaloc. For a while, anything that was abstract and on the scarier side was labelled as Tlaloc. However, in reality, Tlaloc's two main identifiyers are fangs, along with ringed eyes.