It means that the only light in the room is coming from the lamp on the desk.
Answer:
The words, form and shape, are closely related to the words, structure and pattern.
Explanation: Writers of the classical period constructed their works according to a pattern they had learned. They had to be creative within the forms and norms of the period.
Dictionary: Formal (2nd definition) following or according to establised form, custom, or rule. (Merriam-Webster)
Formal: using an agreed and often official or traditional way of doing things. (Cambridge)
From the Italian sonetto, which means "a little sound or song," the sonnet is a popular classical form that has compelled poets for centuries. Traditionally, the sonnet is a fourteen-line poem written in iambic pentameter, which employ one of several rhyme schemes and adhere to a tightly structured thematic organization. Two sonnet forms provide the models from which all other sonnets are formed: the Petrarchan and the Shakespearean.
Dash is the mark of punctuation that can indicate that more info is to come.
Hope this helped :)