What type of sonnet includes three quatrains and a couplet, typically written in iambic pentameter?

The description provided in the question aligns with a Shakespearean sonnet. This type of sonnet consists of three quatrains followed by a final rhymed couplet, and it is traditionally written in iambic pentameter. The structure allows for the development of a theme or argument over the course of the three quatrains, while the couplet often provides a resolution or commentary on the preceding verses.

The other types of sonnets mentioned differ in structure and characteristics. The Italian sonnet, also known as the Petrarchan sonnet, typically comprises an octave and a sestet. The Spenserian sonnet features a unique rhyme scheme that connects the quatrains more closely than the Shakespearean form. Lastly, "Octava Rima" refers to an eight-line stanza often used in narrative poetry, not a sonnet format. Thus, the predominantly outlined components lead us definitively to the identification of the Shakespearean sonnet as the correct answer.