Questions

There were only three people. Son, his father and his grandfather.

The F1, F2 to F12 keys that are found on the top row of most computer keyboards are called as Function Keys. Unless you've witnessed the evolution of computers from their early days, you probably don't know why they were invented and for what.
Function keys were used by various computer programs to fulfill various functions.

F12 - It is used by many web browsers to open the developer tools.

Autotroph: This term means organisms that synthesise their own food. Troph means feeding. Auto means self. The green plants which synthesise their own food are called autotrophs. All others which depend upon the plants directly or indirectly are called heterotrophs.