Should the introduction section of a proposal describe my organization, which will be the applicant? Or should it describe the organization that will be implementing the program?

My organization is seeking funding for a program that will be delivered by another organization. In my letter of inquiry do I provide information about my organization because it will receive the grant, distribute the funds, and oversee program implementation? Or do I provide information about the organization that will actually do the work?
Both. You must provide information about the applicant organization because it will manage the grant and will be responsible for financial management and reporting, and for program implementation. But you must also provide information about your partner organization because its capacity to carry out the work is critical to the proposal's credibility. Any funder will want to know about fiscal management and program oversight, and also about the competency of those doing the work. Clearly define the role of each organization.