The poem begins by personifying Love as a female figure who decides "in heart and deed" to fill the world with "greater joy." Right away, Love comes across as generous and open-hearted. It sounds as though Love is someone working behind the scenes to create a happier life for all humanity.
The phrase "arose in heart and deed" is a bit of a play on words. On the one hand, it describes the personified "Love" figure waking up, but it also suggests love, the emotion, blooming in humanity's hearts and actions. It suggests the warmth and tenderness that "arise" when you have feelings for someone. Falling in love, this line suggests, is like discovering a joy "greater" than you ever knew existed. The phrase "wake the world" likewise presents love as an eye-opening force, one that shakes people out of their everyday stupor.
Next, the poem personifies "Greed" as a male figure who, unlike Love, is only looking out for himself. Sensing that Love has some kind of plan to spread joy, Greed wonders how he, personally, can benefit. He thinks he might be able to "win some costly toy" from Love, a phrase that trivializes love as nothing but a plaything. The need to "win" is totally at odds with the way Love works, while the word "costly" might make readers think of people whose only motivation in life is to accumulate wealth.
In four lines, then, the poem has created a stark juxtaposition. Love is generous and selfless, readily hoping to spread joy through the world. Greed is selfish, seeking material gain and a desire to beat out others.
This stanza also establishes the poem's form. Each stanza is a quatrain, meaning it has four lines. Those lines follow an alternating rhyme scheme (ABAB) and iambic tetrameter (meaning each line contains four iambs, poetic feet with an unstressed-stressed syllable pattern):
When Love | arose | in heart | and deed
To wake | the world | to great- | er joy,
"What can | she give | me now?" | said Greed,
Who thought | to win | some cost- | ly toy.
Do note, that it's possible to scan the "What" in line 3 as a stressed beat, making the first foot a trochee. This slight blip in the poem's rhythm conveys Greed's desperation to take something for himself.
In any case, the poem sounds simple and straightforward. This, along with the personification of the abstract concepts of love and greed, makes the poem easily accessible to children. The poem's formal directness keeps its moral message front and center (and, perhaps, also makes the poem itself easier to commit to memory).