A poem’s line can end before its sentence does. Your eye reaches the margin, but the grammar asks you to continue. That small disagreement between visual ending and verbal movement is the starting point for reading enjambment.
The Academy of American Poets defines enjambment as a sentence or clause continuing across a poetic line break. Knowing the term is useful, but the more interesting question is what that particular break does to your experience of the words.
Try a short original example
I left the window open for the rain
to speak before the room remembered morning.
These lines were written for this explanation. At the end of the first line, “for the rain” can briefly sound like a practical reason for leaving a window open. The next line turns the rain into something that speaks. The break creates a moment in which one possible meaning is held before another arrives.
Now write the same sentence as prose. The grammar remains, but the visual pause disappears. Move the break after “open” and the emphasis changes again. The exercise does not prove that one arrangement is best; it shows that lineation contributes something beyond the choice of words.
Let punctuation and syntax work with the line
Read a poem aloud without inserting a full stop at every margin. Then try a lighter hesitation at the breaks and listen to the difference. Enjambment does not require every reader to rush, nor does it mean every line break must be ignored. The phrase, rhythm and surrounding lines help determine the effect.
On the page, mark one line whose end temporarily changes what you expect next. Ask which word receives emphasis and whether the following line confirms or revises the expectation. An end-stopped line nearby can make the continuing line feel even more mobile.
This is a manageable way into an unfamiliar poem: follow one sentence across its boundaries. You can notice the poet’s choices before trying to settle the meaning of the entire work.