HR:Security Profile and MO:Security Profile are used for MOAC (Multi-Org-Access-Control).
HR:Security Profile is used to restrict the data in Human Resources according to the Business Group or whatever criteria you define in this security profile. Thus, for HR, it uses this secuity profile in its data exposure to the user.
MO:Security Profile acts the same but is used for Financials and Manufacturing applications. It restricts the access (site level or can be set at responsibility level) to certain operating unit (or whatever criteria defined in the security profile).
If there is no value at MO:Security Profile, then Financials and Manufacturing use the HR:Security Profile option for their data exposure to users.