What is the LST for DeFi?

Could you please elaborate on the term "LST" in the context of Decentralized Finance (DeFi)? As a professional practitioner in the field of cryptocurrency and finance, I'm aware of the growing popularity and significance of DeFi, but I'm not entirely familiar with the abbreviation "LST" being specifically associated with it. Is it a new protocol, a token, or perhaps a specific strategy within the DeFi ecosystem? Clarifying this term would help me and others in the community to better understand its application and significance within the broader DeFi landscape. Thank you for your assistance in clarifying this matter.