What is HYDRA's goal? Are they related to SHIELD?

A question about Marvel comics: What is HYDRA's purpose for existence? What is their ultimate goal, or ideal, or motive? They are an organisation, and all organisations are founded for a reason. I am guessing they have more motives than just world domination.

(spoiler) I hear that perhaps HYDRA believe in uniting all of humanity, and improving Earth's technology, as a way of asserting Earth's power in the wider universe. I.E. to protect humanity through superior technology and military force, against alien empires. Is this true? (/spoiler)

Kinda like how the Galactic Empire in Star Wars, according to Expanded Universe material, believed in uniting the galaxy into a single military state, and building the Death Star superweapon, partly because they knew the galaxy was going to be invaded by a hostile alien race. Or how Scorpius in Farscape wanted technology, in order to prevent a Scarran invasion of the galaxy.

Since the Agents of SHIELD TV series is coming soon, here is another question for Marvel fans: How likely is it they will emerge as a main enemy in Agents of SHIELD? Are they related? Are they arch-enemy organisations?

I know what Hydra and Shield is, but I have no idea what you are referring to or what that picture is from......

Are you talking about possible plot twists in a unreleased marvel movie or what Hydra's goals are from the comics?

You know you should have probably provided more context for this post, kinda reads like nonsense the first time through :P

The comics.

To be perfectly clear: I am asking what HYDRA's motive/goal or purpose for existing is - every organisation has a purpose. Are they just general criminals like SPECTRE in James Bond, or do they have some higher philosophical goal than profit or conquest?

The picture is from Captain America: The First Avenger, depicting HYDRA soldiers. Since Agents of SHIELD, the new TV series, is part of the Marvel Cinematic Universe, could HYDRA perhaps turn up as a villain in that show? Are HYDRA and SHIELD related in the comics, like I've heard?

Hyrdra is like Cobra from GI-JOE, they don't really have any motives that are set in stone, they started out as semi-fascists in the 40's and since then have been just plot devices for other comics to draw from.

I don't know anything about Cobra - also as is probably clear from my main post, I don't know much about the Marvel Comics universe (Earth 616 or otherwise). But I guess I see what you are saying - they are just general villains, who change with whatever the writers need. Kinda a waste, because they would make for an interesting counterpart to SHIELD.

They are a counterpart to shield, but Shield and Hydra are what you would call third string in Marvel, they aren't thought about often unless as you say a writer needs a plot device, This is mostly due to the fact that the Marvel Universe has sort of grown much larger around them while they stayed the same for example the Hulk when he was created was only as powerful in terms of strength as any other super strong characters in Marvel since then hes been promoted to one of the strongest characters in Marvel outside of some of the god-tier character.

Basically it's because it's become too hard to write a serious story about Hydra when most Heroes have become almost demi-gods and the only other characters who would come into conflict with Hydra aren't First-String characters anymore either.