This post is intended for people who are new to the world of software testing, meant to provide some context for things you may hear spoken by people around you. You might hear people use the term "shift left" or refer to the olden-days of QA when Dev teams would "just throw their work over a wall".
These phrases are a reference to a general trend which has taken place in the SDLC (Software Development Life Cycle), which is a fancy way of saying "how companies make software". Essentially, Dev and QA teams used to be quite separate, and software testing was mostly done manually.
These days, as QA teams take on more automation responsibilities, it makes more sense for them to sit closer inside the walls of the Engineering organization. The term "shift left" means that under this new paradigm, QA's involvement comes earlier in the timeline of a feature's release, beginning testing alongside Dev, not once all their work is done.
The term SDET (Software Development Engineer in Test) represents a desire by many to pull QA entirely inside the Dev team. I believe that in general, this is good for the world of software testing. It requires QA Engineers to become more technical than their manual "Analyst" counterparts, but that also means higher salaries and more interesting work. There will always be some manual work in software testing, but less and less over time.
For managers, it also makes managing teams easier, and for some companies, allows the creation of "squads" in which a few developers are paired with one or two QA and can tackle projects or product features as a team.
Right now is a great time to get started working in QA, and we're finally getting treated as a core part of Engineering. If you're new to the industry, I hope this inspires you to pick up some test automation skills and ditch the "Analyst" title for "Engineer". The shift left really has been good for us.