A cell invaded by a virus is called a host cell because it provides the virus with the resources it needs to replicate. Here's why:

* Resources: The host cell supplies the virus with building blocks like amino acids, nucleotides, and energy sources necessary to create new viral particles.

* Machinery: The host cell's ribosomes, enzymes, and other cellular machinery are used by the virus to translate viral genetic information into proteins and replicate its genome.

* Environment: The host cell provides a controlled and stable environment for the virus to survive and multiply.

In essence, the virus is a parasite that relies on the host cell to survive and propagate. It's like a tenant living in a house (the host cell) and using its resources to survive and create more tenants.