Christopher Marlowe died at the ripe old age of twenty-nine years old, which didn't give him a particularly lengthy career as an author. He was also more focused on drama than on poetry, so that makes pinning down his poetic style a difficult task. Luckily, there are a few things that characterize his poetry, one of which is his use of rhyming couplets. A rhyming couplet is a term for two adjacent lines of poetry that, you guessed it, rhyme. These lines appear one right after the other in a poem, so the whole poem will end up with a rhyme scheme that looks something like this: AABBCCDD etc.
Marlowe eventually became famous for writing the poem "Hero and Leander," a work which many scholars say totally revolutionized the use of heroic couplets in poetry. Now a heroic couplet is a special kind of rhymed couplet, one that uses iambic pentameter as opposed to iambic tetrameter like we see in "The Passionate Shepherd". But "The Passionate Shepherd to His Love" is one of the earlier works of Marlowe's career—one of the building blocks of what would eventually become one of Marlowe's greatest successes.
One reason "Hero and Leander" was so successful as a poem written in heroic verse is because Marlowe manages to make the poem flow and rhyme without reducing it to a sing-songy type of beat. He does this by using enjambment (which we see in lines 2-4 of "The Passionate Shepherd"), alliteration (see lines 1-2, 5-6, 8, 18, 20-24), consonance (in lines 3-4, 7-8, 9-10), and assonance (in lines 1, 4, 6, 7, 18, 20, 24). Marlowe is certainly not the only person to employ these poetic devices, nor he is the only one to write in rhymed or heroic couplets, but he definitely changed the game for Renaissance poets. If you're reading something from the 17th century and it's written in heroic couplets, chances are you're reading the work of someone who was seriously influenced by Marlowe.