A security lending program is where a broker-dealer (Apex Clearing Corp) lends fully paid stocks or other securities to an investor who is short selling those securities. The broker-dealer will loan out stocks/securities from other investors that have purchased and fully own the stocks/securities.
When your stock/security is loaned out, you do not see any changes to your investment. There are some risks with share lending, for instance, they are not insured by SIPC.
For more information, please refer to this article from SoFi Learn: What is Share Lending?