In one sentence
PerplexityBot is the web crawler operated by Perplexity AI. Perplexity uses it to search the web in real time when generating answers.
What does it look like in practice?
For example, when you ask Perplexity a question, PerplexityBot searches the web in real time and returns something like:
[Answer body]
Sources: ○○ Research, △△ Report