A virus uses its fibers (projections) to latch on to the things on the outside of the cell. What are those things called?

Receptor

Explanation: A virus can latch onto a receptor, which gives it access to attach and inject their genetic material.

When a virus infects a host cell, it uses the cell's machinery to make copies of its own genetic material in a process called replication. finally, during the process of self-assembly, that protein shell and the copies of the virus's genetic material are assembled into new viruses.