Line breaks are where natural pauses occur in the writing, and signal a change of movement; they can also emphasize certain lines to make them more important or intense than others.
Line breaks, in general, make a poem more interesting and dynamic. For example, Charles Bukowski wrote
“Love breaks my bones
and I
laugh.”
The word “laugh” is on a separate line by itself to get more emphasis; it makes those three lines even more intense.
Put in breaks where you would pause naturally if you were reading the poem out loud, or where you want to emphasize a certain section or bit. Put in breaks where you think they will sound good and flow naturally.
Line breaks don’t necessarily “mean” anything; they’re just a nice poetic tool that can make a piece much more powerful and unique.
I hope that helped! :)
P.S. And yes, it’s called “enjambment,” if you’d like to read more about it.