It can be getting way to distracted from the things I need to do, or want to do, mulling over some problem that isn't really a priority at that exact time.
It can be a problem or issue that is a priority, but I don't get to the point of it because I overthink, see too many of the less probable scenarios, too many of the less relevant perspectives, and it becomes a bit to much for me to get a good grasp of after a while, so that I can't see clearly and wade through possibilities, unable to choose one to go forward with.
It can be thinking about things over and over, even though I have decided on a conclusion (often being that I can't solve the problem, and must learn to accept that), turning over every little coin hoping to find a microscopic key that might solve things, or not even hoping for that, but just itching on a scar that never get to heal properly, over and over.
What makes it overthinking rather than just thinking a lot is when it makes me feel bad without leading to anything good, or when it is too timeconsuming, so that other things in my life suffer too much, or when the thinking clouds things (from too many aspects, choices, above what my mind can handle and weed out the path forward from). Thinking a lot about something when I have time and find some random thing interesting isn't a problem, or when I really have a problem that needs solving and let that problem occupy my mind and analyse it from many angles, even if it makes me feel bad, as it needs to be done.
Feelingswise it is often anxiety involved, but can also be loss, or shame or guilt. Sometimes also positive feelings, getting exited and using all the energy on puking up a million possibilities and then not having any left to sift through them, any less doing anything.