Site Reliability Engineer - I’m one too lol. Most of what you do is work with dev teams to make sure their service is reliable, then slap an SLO (service level objective) to make sure their service meets a certain threshold of reliability.
It's going to vary based on the company you're with but a typical day for me includes reviewing/writing code, attending some meetings for projects, and answering pager duty when something goes boom. Occasional post-mortems and active maintenance of systems. I was up until last week an SRE at a firm maintaining an industrial information system and related services.
