What is the structure of Spenserian Sonnet?

A Spenserian Sonnet, invented by Edmund Spenser, consists of 14 lines. The term "quatrain" refers to a grouping of 4 consecutive lines. Spenserian Sonnets are formed of 3 quatrains followed by a couplet. The rhyme scheme is as follows:

Quatrain 1:A-B-A-B Quatrain 2: B-C-B-C Quatrain 3: C-D-C-D Final Couplet: E-E

Because the ending rhyme in one stanza carries over as the beginning rhyme in the next stanza, some people also refer to this form as the linking sonnet. Often poets try to connect not only these rhymes but also the thoughts as they link from quatrain to quatrain.
Each line follows a meter of iambic pentameter, meaning there are five pairs of syllables (or ten syllables total) per line and that the second syllable in each pair is stressed.
The purpose of the sonnet is to develop an idea, metaphor, conflict, or question, and to shift toward commentary of that purpose in the final couplet.
Below is an example of a Spenserian Sonnet, written by Edmund Spenser himself:

Sonnet 75
One day I wrote her name upon the strand;But came the waves, and washed it away: Again, I wrote it with a second hand; But came the tide, and made my pains his prey.
Vain man, said she, that dost in vain assayA mortal thing so to immortalize;For I myself shall like to this decay, And eke my name be wiped out likewise.
Not so, quoth I, let baser things deviseTo die in dust, but you shall live by fame: My verse your virtues rare shall eternize, And in the heavens write your glorious name.
Where, when as death shall all the world subdue, Our love shall live, and later life renew.