Hi,

The recruitment module consumes models like hr. applicant and hr.job etc. In the case of hr.job that is related to the jobs under the session we can set up each job and their related data. under these job positions. There are different types of applications will come under each job position. so based on that application that is stored in the hr.applicant model. the hr.applicant model will filled by the job form (from the website) or the admin or the related user can add/ create new records in the hr.applicant model.
These models contain each applicant's record, that's why odoo names the model like hr.applicant.
For more reference you can refer  to the link:
https://www.cybrosys.com/blog/main-features-of-odoo-15-recruitment-module

Hope it helps