Different Types of Jacks (Connectors)

"What is the function of these sections (tip, ring and sleeve)?"

They carry the signal. Google audio connector terminology.

Wikipedia is quite helpful on the subject

http://en.wikipedia.org/wiki/Audio_connector

Alternatively try a Google search using either specific connector (jack) names and types or groups (eg - "Audio connector types").

_{Jack - Yet another different kind of jack}

@ Above posts

Googling the subject or wiki-ing it was the first thing anyone does (usually). I couldn't find a site which exactly explains what the specific functions of those sections (tip, ring,sleeve) are and why we even need them, or for that matter which some connectors are TRS, while others TS or TRRS.

Can two different jacks of the same size and type (TRS, TRRS etc.) be used in place of each other for carrying a signal? My guess is, it can't (I don't have jacks in my house to test). But then if it can't then can anyone tell me why not?

Can two different jacks of the same size and type (TRS, TRRS etc.) be used in place of each other for carrying a signal? My guess is, it can't

That is correct.

But then if it can't then can anyone tell me why not?

Again, the simplest explanation is available on Wikipedia.

http://en.wikipedia.org/wiki/TRS_connector

I don't see where the article explains the answer to my question you quoted in italics.

Again, the answer (including pictures and a detailed explanation on the different parts of the plugs) is located here

http://en.wikipedia.org/wiki/TRS_connector

Look at the section marked "Tip/ring/sleeve terminology"