* Ultimate Origin: Spanish, along with Portuguese, Catalan, Romanian, and many others, ultimately descends from Latin, the language of the Roman Empire.
* Vulgar Latin: Latin evolved over time and different variations arose. The specific form of Latin that gave rise to Spanish is known as Vulgar Latin. This was the language spoken by ordinary people in the Roman Empire, as opposed to the more formal, literary Latin.
* Castilian: As the Roman Empire declined, Vulgar Latin continued to evolve in different regions. In the Iberian Peninsula, specifically in the area around Castile, a dialect emerged that eventually became known as Castilian.
* Modern Spanish: Castilian, through a long process of development, became what we know today as Spanish.
So, in summary, Spanish is descended from Latin through the evolution of Vulgar Latin, with Castilian as a key intermediary step.