True about precision attachment:
Internal attachment / precision attachment - Means interlocking device, one component of fixed into an abutment or abutments + other integrated to a removable prosthesis to stabilize and/or retain it
Semipresicion rest- Rigid metallic extension of a fixed or RPD + fits into an intracoronal preparation in a cast restoration.
One intracoronal preparation in tooth + one integrated into RPD prosthesis to stabilize and / or retain it
One intracoronal preparation in tooth + one removable attachment to prosthesis
One intracoronal fixed on abutment + one integrated into RPD prosthesis to stabilize and / or retain it
All of the above