Profile Base Permission and permission from permission set.(Generally we gwt option to give permission of field to the profile which is base permission to the profile))

Let me explain the permission hierarchy in Salesforce when it comes to field-level security (FLS):

When both Profile and Permission Set have different levels of field access:
1. The most permissive setting wins
2. Permissions are additive, not restrictive

So in your scenario:
- If you give READ access in the Profile
- But NO access in the Permission Set
- The user will still have READ access to the field

This is because:
- Permission Sets are designed to grant additional access, not restrict it
- They can't be used to revoke permissions that are already granted at the Profile level
- The user will retain the READ access from their base Profile, regardless of the Permission Set settings

To completely restrict access to the field:
- You would need to remove access at both Profile AND Permission Set levels
- Or remove access at the Profile level, since that's the base level of access

Best Practice:
- Keep minimal permissions in the base Profile
- Use Permission Sets to grant additional access when needed
- Don't rely on Permission Sets to restrict access that's already granted in the Profile