Explanation
Box 1: IsBlank
The IsBlank function tests for a blank value or an empty string. The test includes empty strings to ease app creation since some data sources and controls use an empty string when there is no value present.
Box 2: IsType
The IsType function tests whether a record reference refers to a specific table type.
Box 3: AsType
The AsType function treats a record reference as a specific table type, sometimes referred to as casting. You can use the result as if it were a record of the table and again use the Record.Field notation to access all of the fields of that record. An error occurs if the reference isn't of the specific type.
Box 4: AsType
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/functions/function-isblank-isempty
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/functions/function-astype-istype
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/functions/function-astype-istype