They all have 14 lines. :)
-Apex-
The most common sonnet forms are the Petrarchan (or Italian) sonnet and the Shakespearean (or English) sonnet. The Petrarchan sonnet consists of an octave followed by a sestet, while the Shakespearean sonnet is composed of three quatrains and a final rhymed couplet.
Iamp
Yes, sonnets typically have a fixed form with 14 lines, a specific rhyme scheme, and a defined structure. The most common sonnet forms are the Petrarchan (or Italian) sonnet and the Shakespearean (or English) sonnet.
Love and the impermanence of beauty are common themes.
Shakespearean sonnets - sonnets by Shakespeare
This is akin to asking whether the Pope is Catholic. Shakespeare is the second-most famous writer of sonnets in the world (after Petrarch).
Sonnet 16 Most sonnets are famous
Pentameter
the joys and sorrows of love.
Shakespearean sonnets - sonnets by Shakespeare
I am not sure which sonnets you are asking about; many poets wrote sonnets, 14 lines of poetry usually about love (whether losing it, longing for it, or being happy to have it). If you are asking about Shakespeare's sonnets, by most accounts, he wrote 154 of them. Without more information from you, I have no way of knowing which sonnet I should explain.
William Shakespeare is best known for his sonnets. Shakespeare published a total of 154 sonnets. Sonnets contain fourteen lines with a specific rhyme scheme.