What exactly is a research specialization as opposed to a regular tech?

Are you referring to things like right after Manufacturing Collective you get 3 research choices. One for +10% production, One for +10% research, and another one that reduces costs by 10% (I think).

If I'm following your train of logic and am right about what you are referring to then you research one of these 3 and the next tech in the tree opens up. However the 2 you did not research remain there. From your phrasing it sounds like you think you can no research the other two without losing the one you had before. But these are cumulative options. You can have  all 3 if you choose to invest the research time.

If I have miss understood you then apologies but you are extremely vague about what you are referring to.

Both of you are correct!  A specialization tech (rounded tech bubble) gives a choice of 2 or 3 options.

• You need to complete only 1 of them to unlock deeper techs in the tech tree (except across an Age boundary).
• You can research as many as you like (even all 3), but there's tech cost inflation to consider.  See below.

No, you cannot change a specialization.  However, you can freely research the others (if you want).  Word of warning, though: tech cost inflation is insidious.

• For each tech level you complete:
  
• Every other tech (in the entire tree) gains a small creep cost.
• Every downstream tech (in the same subtree as the one you just finished) gains a large creep cost.
• We don't know what the formulae are for these costs, but we think the "large" cost is exponential.  The "small" cost might be only (supra)linear.

These creep costs really add up.  You can measure this objectively if you ever get a random free 25% research bonus to a brand-new tech from surveying an Artifact.  Ignore that tech for the next ~100 turns while you research other stuff.  It will decay down to 5-8% of its bubble (measured in pixels).  What that really means is that all other tech costs increased by up to ~400% of what they were when you got the bonus.

Hence:

• Taking all 3 specializations of one specialization tech makes the subtree after it significantly more expensive.  A leaner-meaner empire that took only 1 and beelined past it might outrace you to the higher techs, and kill you first (or get Technological Victory first).  Paul has said that this system is designed to suggest that you choose only 1 each, while not being an outright game restriction.
• A leet exploit in the Warfare subtree is: commit to one weapon type (of 3 types) for your empire ... and then take the specialization (Augment?) of a different weapon type, just to minimize the research costs of your chosen subtree.  You really might benefit more from reaching, say, level 7 in your weapon tech when your opponents are still only at level 6 + a wimpy specialization.

Yes, you can research as many specializations as you can find. I would not recommend it though.

I've found that there are many techs past specializations that are worth researching. Focusing on nabbing more specializations than you need can be a distraction. For instance, the tech needed to enable tourism is not a specialization. Tourism is a new source of income (that you don't start the game with) that does not require you to divert production to get. Bigger ships are very useful. Planet improvements to get more population, and planets improvements to boost morale is useful. Many planet improvements can be placed multiple times (so you get the benefit multiple times), but bonuses from specializations is applied only once.

Do you get what I'm trying to say?

I guess I'm confused by the way it's structured.  There's regular square techs, and then there's rounded specializations, where if you click it it opens up into three.  Is there any real difference between a normal technology and a specialization?  

I haven't seen any real mechanically difference between normal techs and specializations. Aside from the multiple choice part, the only difference that I've seen is in the way they have been used thus far. The specializations might offer things like smaller weapons, cheaper weapons, or better weapons (offered in percent improvements). For instance, a specialization might reduce the size of all missile weapons by 20%. Normal techs tend to offer new things instead of improvements to existing things. For instance, they might unlock stingers or harpoon missiles.

I suspect that if you wanted to mod things, you could make the specializations unlock different ship parts and planet improvements, and make the normal techs give bonuses only. I'm not a modder, but I think you could make a line of techs that combine all weapon techs into one branch. With that branch, you might be researching weapon techs in general, and for each specialization, you choose if you want lasers, railguns, or missiles. Each of the normal techs might simply be percent increases to firepower or something.

You just noticed specialization techs...now? How many hours, or even turns have you actually played?

I noticed them of course, and have been playing with them so far without understanding exactly how they differ from regular techs, so I asked.