Bitcoin mining rigs solve complex math problems to compete for the right to update the ledger. They usually contain mining chips (ASIC), heat sinks and fans. A mining chip (ASIC) is the core component in a mining rig. Rigs can get overheated during the mining process hence heat sinks and fans are installed for cooling purposes.
As mining is essentially a competition of computing power, miners who have more powerful rigs have higher chances of receiving bitcoins as a reward.