It means a confidentiality agreement. When you ask the seller to disclose detailed materials that are not included in the property summary, you will often be asked to submit a confidentiality agreement. For example, materials such as rent rolls containing the details of the lease agreement and the repair history of the building can only be disclosed after the CA has been submitted.
In other industries, such as the M&A industry and the IT industry, it is often referred to as a Non-Disclosure Agreement (NDA).