| Term | Definition |
| Transistor level | Lowest level. Deals with transistors and their connections to form a circuit. |
| Gate level | Above transistor level. Deals with logic gates and their connections. Can be expressed using a Boolean equation of a truth table. |
| Truth table | A table of all inputs and all possible outputs. |
| Register-transfer level | Above gate level. This level deals with how data is transferred between registers and functional units to solve a problem. |
| Behavioral level | A description of the entire circuit. Can be done in VHDL. |