Easiest/Simplest way to link two fields across two standard modules such that when updated in 1 it updates in other?

Easiest/Simplest way to link two fields across two standard modules such that when updated in 1 it updates in other?

Hey all,

I know this is too simple an idea to be so complicated in finding an answer. Ive read a variety of posts, etc that are similar but not exact. I'm not sure if i need a lookup field, deluge script, workflow, other, what combo of those, etc

Question- 1. How do I link a field in 2 standard modules such that when it is update in one module, it updates/overrides the field in the other module? 

1a. Is there a way to make this one-way relationship or does it have to be bilateral? 


Specific example: Modules: Task and Leads

If I want to update "Lead Status" in a lead record but from within a Task associated with that record, how do I do so?
What is the easiest way possible?

Is it as complicated as needed to create an identical field "Lead Status" in tasks module and writing a script to overwrite the "lead Status" in a lead record when its updated in tasks module? (Mind you I dont know how to write deluge, though I understand the logic of it and can read a simple script)