Other Acronym's

YAGNI - You Ain't Gonna Need It
means don't add functionality that you don't need.

DRY - Do not Repeat Yourself
means don't copy and paste the same bunch of code, try to abstract it out.

KISS - Keep it simple, Stupid!
simplicity should the key goal in design and unnecessary complexity should be kept out.

what is SOLID?

SOLID is OOP Principle terminology/acronym. It stands for the below

S - Single Responsibility Principle (SRP)
O - Open/Closed Principle (OCP)
L - Liskov Substitution Principle (LSP)
I - Interface Segregation Principle (ISP)
D - Dependency Inversion Principle (DIP)

S/SRP means a class should be responsible for one task/objective
O/OCP means software entities should be open for extension and closed for modification
L/LSP means objects in a program should be replaceable with sub-types without breaking the program
I/ISP means many client specific interfaces are better than one general interface
D/DIP means Depend on abstractions and not on concretions/implementations [Dependency Injection]