Why does NASA say SOL?

Could you please clarify for me why NASA uses the term "SOL" in its communications? Is it a specific abbreviation or acronym related to space exploration? Does it stand for a particular concept or measurement within the field of astronautics? I'm quite curious to understand the significance and relevance of this term in NASA's operations and how it contributes to their mission objectives. Could you elaborate on its usage and context within NASA's vocabulary? Thank you for taking the time to explain this to me.