Corporate recruitment is often also referred to as internal recruitment. It is the process through which a company uses recruitment staff that they employ to find applicants for roles in the same company. Corporate recruitment is the opposite of using a recruitment firm to fill vacant positions.
The candidates for these roles may either be internal or external, but the people doing the recruiting are internal staff. Corporate recruiters usually write job descriptions and job ads and advertise the roles for their company. They manage the recruitment process including defining screening and assessment methods to be used. They may then interview the applicants, often alongside the hiring manager.