Component assembly is the process of attaching electronic components to a circuit board. This is typically done by hand, using a soldering iron, and requires a high level of skill and attention to detail to ensure that the components are properly placed and connected.

Soldering is the process of joining two pieces of metal together by heating the metal to its melting point and using a filler material (solder) to create a strong bond. In electronic assembly, soldering is used to attach electronic components to a circuit board.
The soldering process typically involves heating a small area of the circuit board and component leads with a soldering iron, and then applying a small amount of solder to the heated area to create a strong mechanical and electrical connection. Soldering is a critical step in the electronic assembly process, as it ensures that the electronic components are properly connected and will function as intended. Improper soldering can cause poor electrical connections, which can result in malfunctioning or non-functioning electronic devices.
It's important to use the right temperature and the right amount of solder, and to ensure the components are clean before soldering.