From such a simple description, there are multiple possible approaches. The details you haven't shared may dictate one approach as a better option than another.
A calculation field can return different values for field 2 based on the value of field 1:
Case ( Field1 = "A" ; "Apple" ;
Field1 = "B" ; "Bannana" ;
and so forth.... )
A related table can store the values you want to conditionally display and then Field 1 can be a match field in a relationship:
MainTable::Field1 = LookUpTable::Field1
And then you could have a number of records in LookUpTable with values such as:
Field 1 Fruit Field
You would then place the Fruit Field from LookUpTable on your MainTable layout to conditionally display your data.
The calculation may be a bit easier to set up, but if you may need to modify what data is conditionally displayed from time to time, the lookup table can be edited as a simple data entry task where changing the calculation requires someone with developer skills to redefine the calculation.
I have a similar question, but let me write down what I'd like to achieve:
I have a drop-down box (in fact a simple "static" selection).
If one of the values pop's up (let's say "Education"), I'd like to show another field, containing a related selection with the "Courses" one could choose (At this moment, I don't care yet, whether the second "conditional field" is another Static Selection or fields showing from a table).
Is that possible?
If so, can anyone explain how to achieve this?