Here's a definition of pantheism from dictionary.com:

the doctrine that God is the transcendent reality of which the material universe and human beings are only manifestations: it involves a denial of God's personality and expresses a tendency to identify God and nature.

Some people think that panteism means that everything is God; since the very concept of "God" is subject to so many different readings, I think this is a better way to look at it.  Everything in the world is a manifestation of God, and each of us has the transcendent ability to understand this reality; it's a knowledge that is not limited to Locke's knowledge.through.the.senses.  It also echos the concept of "The Two Scriptures": that God is revealed to us through the Word in Scripture and through direct manifestations through nature made available to us all.

Clearly Wordsworth connects with nature in a way that gives him life that life in the city (the antithesis of nature) cannot give him.  He is renewed just by being in the presence of nature.  This somewhat lengthy quote makes it clear:

These beauteous forms,
Through a long absence, have not been to me
As is a landscape to a blind man's eye:
But oft, in lonely rooms, and 'mid the din
Of towns and cities, I have owed to them
In hours of weariness, sensations sweet,
Felt in the blood, and felt along the heart;
And passing even into my purer mind,
With tranquil restoration:--feelings too 30
Of unremembered pleasure: such, perhaps,
As have no slight or trivial influence
On that best portion of a good man's life,
His little, nameless, unremembered, acts
Of kindness and of love.

I hope this is simple enough.