Hardware is the component that performs the hash calculations.

There are different types of hardware:

ASIC (Application-Specific Integrated Circuit): designed to perform a single task with maximum performance
CPU (Central Processing Unit): designed to handle a wide range of tasks, but not at maximum efficiency for any specific one
GPU (Graphics Processing Unit): designed to perform a large number of calculations in parallel
FPGA (Field-Programmable Gate Array): designed to be reconfigurable hardware, adaptable to different tasks

In mining:

ASIC: maximum energy efficiency for a single algorithm
CPU: mainly used for algorithms designed to be ASIC-resistant
GPU: flexible, capable of mining many different coins and algorithms
FPGA: a balance between efficiency and flexibility, but less commonly used

For comparing and viewing ASICs miners, a useful resource is: AsicMinerValue
And for ASICs, GPUs, CPUs and FPGAs, a useful resource is: HashRate