Wordsworth's poem is rather straightforward, written in language that most everyone should understand. So rather than try to paraphrase the poem word for word, I'll explain briefly what each stanza is saying.
I wandered lonely as a cloud
That floats on high o'er vales and hills,
When all at once I saw a crowd,
A host, of golden daffodils;
Beside the lake, beneath the trees,
Fluttering and dancing in the breeze.
Simply, the author is walking near a lake when he comes upon a "host," or large bed, of daffodils. "Vale" is another word for "valley."
Continuous as the stars that shine
And twinkle on the milky way,
They stretched in never-ending line
Along the margin of a bay:
Ten thousand saw I at a glance,
Tossing their heads in sprightly dance.
There are as many daffodils as there are stars in the sky--so many they can't be counted. He says in one glance he can see "ten thousand," which is a large number used to express how large the bed of flowers is. They seem to be dancing in the breeze.
The waves beside them danced, but they
Out-did the sparkling leaves in glee;
A poet could not be but gay,
In such a jocund company!
I gazed—and gazed—but little thought
What wealth the show to me had brought:
The waves of the lake lap at the shore, but the sound the daffodils make as they dance in the wind outdos the sound of the water. The poet can't help being happy when he is in such joyful (jocund) company. He looks at them for a long time, but he doesn't yet appreciate what experiencing these flowers has done for him.
For oft, when on my couch I lie
In vacant or in pensive mood,
They flash upon that inward eye
Which is the bliss of solitude;
And then my heart with pleasure fills,
And dances with the daffodils.
Now, in the final stanza, the poet knows how much the flowers have affected him. Often, when he is lying on his couch or when he is in a thoughtful (pensive) mood, an image of the daffodils will come to him, and then his heart fills with pleasure and "dances with the daffodils."
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