Add You can call const member functions on const objects. Non-const functions are forbidden on const objects. This prevents accidental modification when you pass objects by const reference.
Getters should usually be const since they just return data without changing it. Setters cannot be const since they modify members. Understanding this concept deeply will help you write better code.
Practice with examples until the pattern becomes automatic. Review earlier sections if anything is unclear. Building on solid foundations makes advanced topics easier.