What do you mean by the backbone of the company?

Core members and key roles.

The backbone of a company refers to the core members who play a key role in the organization and have important skills and knowledge. It bears important responsibilities and plays a vital role in the operation and development of the organization. Key employees have key skills and professional knowledge, showing a high sense of responsibility, leadership and stability. Influential, able to work with the team and promote the success of the organization.