The short answer
You have a search page open with fifty people on it and you need them in a CSV before the call. Here are three common ways. Type the names out, one at a time. Run an extension that works through the site for you, which is the kind of tool the site's help names as a reason to restrict an account. Or read the page as it sits on your screen, which is what Rensa does.
The three ways, and what each costs
Typing is slow, and copying from a page you already have open adds nothing for the site to see. An extension is faster, and leaves the pattern the site restricts. Its help page says "You may be restricted from viewing additional pages if we detect an unusually large number of page views from your account". Reading the screen is fast too, and puts nothing in your browser for the site to find.
How Rensa does it
Rensa is an app for your Mac or your Windows PC. Pick the window to read. Whenever there are people on your screen, press one shortcut, and each of them becomes a lead with their name, title, company and location. Rensa captures what you see and reads the leads out of it. Nothing is installed in your browser, nothing runs inside any site, and Rensa never sends a request to a site at all.
The CSV
Every list downloads as a CSV with every field. Each lead is a line with the name, the title, the company and the location as read, and the moment it was read. The file opens in Excel, Numbers and Sheets as it is, and imports into any CRM. Rensa can also send the list straight to HubSpot, Pipedrive or Salesforce. Your enrichment tool adds the email and the rest from there.
What you decide on
A lead Rensa isn't sure about is marked as needing a look, and the list won't go until you've kept it or dropped it. The same person read twice in one sitting counts once. Two leads from different sittings that look like one person are merged only when you say so. Nothing Rensa was unsure about reaches the CSV until you've decided on it.