"exec" re-executes your script manually.
When Blockland starts up, it converts all file.cs files into machinecode (i think .dso?) and loads them into its cache. If you change your file.cs while Blockland is running, and then call your function from the console again, it will execute the cached version (the old one).
Exec reloads your file.cs into Blocklands cache.
If you're a beginner, your Blockland will crash regularly from reexecing scripts due to wrong syntax. If that happens, and you want to check what the f*ck happened, open the console.log in your Blockland folder and scroll down till the end of the file. The console.log (open it with notepad for example) is a log of what Blockland did while it was running, stuff like echo("test test"); will appear in this log.
The %obj.dump(); function might be of some use to you, too. It writes all related functions to that object into the console, and therefore into console.txt.
%obj is a variable, the . indicates that dump is called on %obj.
%obj could be a client number for example or a number of an object (vehicle/player maybe)
Try looking at a vehicle, enter /getid into the chat, memorize the number as %number and enter %number.dump(); into your console. Magic happens.
Vehicle example:
%number.addVelocity("0 0 10");
("0 0 10") is a 3d vector, with x=0, y=0, and z=10. Therefore to your vehicles velocity will be added 10 units of speedstuff in the positive z direction, which would be upwards.
For the other basic script stuff just visit the Coding Help section of this forum and look through all sticky threads, also General Modification Help theres a Topic labeled 'Big list of tutorials'