When numbers get very large or very small, writing them becomes problematic. For example, it is difficult to tell the difference between these following two numbers without counting zeros:
0.000000000000000234 and 0.00000000000000234
Similarly, it can be difficult to immediately see the difference between
12000000000000000 and 1200000000000000000
To avoid confusion (and miscommunication) scientists use scientific notation.
The idea behind scientific notation is relatively easy to understand.
The process of doing math with scientific notation requires you to understand how your calculator understands what you enter and to recognize what it is showing when it displays a value in scientific notation.