That's a star, baby! Or, well. almost.
The funny thing about stars is that they are remarkably simple. They're spherical plasma in a vacuum! Sure, they have all sorts of fun physics in the core, and stellar atmospheres are an incredibly complex environment, but as soon as you leave their immediate vicinity they become extremely easy to study.
You wanna know the best part? 90% of the time, knowing one specific thing about a star is enough to tell you everything you'd ever want to know.
It turns out that when you get a whole bunch of hydrogen all in the same place, it tends to act pretty much exactly the same as the same amount of hydrogen elsewhere. It makes sense, when you think about it - if you copied the Sun and pasted it on the other side of the galaxy, it would still look the same, right?
But let's talk about that 90% first. Baby stars are funky lil guys. They've got all sorts of weird fluid dynamics and temperature gradients and accretion and hoo boy are they neat but they are anything but simple. Turns out that about 5% of the star's lifespan is spent in this "protostar" phase. After that, they tend to settle down and just vibe for a while. When a star is vibing, we say it's "on the main sequence" (more on that later). Eventually though, it'll run out of usable hydrogen in the core and start getting funky again. These are the red giants and such that I'm sure you've heard about before, and about 5% of the star's lifespan is spent here in the retirement home before it either fizzles out or dies.
5% weird at the start, and 5% weird at the end. For that 90% in the middle, stars are very well behaved. Thriving. In their lane. Positively vibing.