It's the web browser for sure (Firefox).
On my laptop provided by work then I guess the most vital program is the VPN client to connect to our server, and then once I'm logged in it's the ERP software, Outlook, and Excel (ugh) that I spend all of my time in.
When I had more time for hobby projects, I'd always have Emacs running on my MacBook with something to work on, and I'd spend quite a bit more time in the terminal. But really these days my MacBook is more of a paper weight than anything else. I spend the whole day on a computer at work when I'm not travelling or out on sales calls. Evenings/weekends I try to keep away from my computer. Any browsing/emailing/messaging I need to do can be accomplished on my phone. My MacBook Air is a 2013 or 2014 IIRC, still going strong, but whenever it kicks the bucket, I'm not sure if I'll even bother to get another laptop of any sort.