I have this in my options
a:4:{i:0;s:10:"Test";i:1;s:12:"FMy Files";i:2;s:7:"Walmen ";i:3;s:15:"Testing on the roof";}
How do I read or interpret it?
Does it floow have a certain criterion?
What is it called?
This is not JSON (notice the semicolons). This is serialized PHP data. You shouldn't have to do anything with it, and certainly not edit it (as you've obviously done, I guess to anonymise it): this is generated by PHP and should only be manipulated by the proper script. It contains metadata about itself, for data integrity checking, I think: Types and Lengths.
$x = json_decode($jsonEncodedString);
Update: After I read the code more closely, it seems, that this isn't JSON. This may be serialized PHP as @passcod already mentioned, but its broken. For example the segment s:10:"Test" describes a 10-characters String with content Test, that is obviously wrong. Simply unserialize() will fail. Dont know, where you get this from, but you should repair "the creator".