A 5 ohm conductor provides 5ohms of resistance in a circuit - making it harder for a current to flow.
First of all, a conductor is simply any material or component of a circuit that conducts electricity (allows electricity to flow through it).
Resistance can be classified as anything that makes it harder for current to flow through a circuit. As a charge (electrons) flows through a component, some of them may collide with the ions in the conducting material. This makes it harder for the current to flow, and therefore causes resistance.
A common factor that increase resistance is temperature - it causes the conducting material's atoms to move more, increasing the chance of a collision. However, different types of materials are affected in different ways. Thin wires usually have more resistance than this wires, as electrons are more likely to collide with ions.
Resistance affects the voltage and current of a circuit, as expressed by the formula:
This means that a conductor of five ohms will have V/5 amps of current. In other words, for a set voltage, the higher the resistance, the less current able to pass through a circuit.
Hope this helps, feel free to leave me a note if I've left anything out, or it is at the wrong sort of level.