Describe the main characterisites of viruses in brief.

Explanation

### Step-by-Step Solution:

1. **Lack of Cellular Structure**:
- Viruses do not possess a cell membrane or cell wall. Instead, their structure is often covered by a protein coat known as a capsid, and some viruses may have an additional lipid envelope.

2. **Dependence on Host Cells**:
- Viruses cannot reproduce or divide on their own. They require a host cell to replicate. This means they invade living cells and hijack the host's cellular machinery to produce new virus particles.

...