Enjambment is the continuation of a sentence or clause over a line-break. If a poet allows all the sentences of a poem to end in the same place as regular line-breaks, a kind of deadening can happen in the ear, and in the brain too, as all the thoughts can end up being the same length. Enjambment is one way of creating audible interest; others include caesurae, or having variable line-lengths.
Mimi Khalvati's 'Don't Ask Me, Love, For That First Love' shows enjambment in its various strengths; the second line, ending at the same time as the sentence, is completely end-stopped, but "What had summer / to do with sorrow in full spate?" is fluidly enjambed. However, the pause for the comma at the end of the fifth line means that the enjambment is less pronounced here. The poet's skill with enjambment is one of the ways in which she keeps her short-lined stanzas, rhymed abab, from jangling unsophisticatedly.