Reconstructions, Archaeotechnique, Experimental Archaeology - what is all this?

Let us start with the definition of archaeotechnique. This is the research into and the use of old craft procedures and other techniques, including their demonstration (for instance in museums). Archaeotechnique also includes the re-making of objects found in archaeological excavations. 

It's a reconstruction as soon as there is part of the object, or part of the information, missing. This applies both to objects and techniques or methods. Once more or less of the item or process are lost, these parts have to be filled in. For example: a textile find is to be reproduced, and colour analysis has resulted in information about the dyestuff used. However, it is not possible to tell how intense the colour was, or its exact hue. Similar finds, other sources such as images or texts, and ethnographical data can help making the guesses in a reconstruction more informed, but there is no way to prove that the result is absolutely identical with the original. Even if the reconstruction is tested in practice and works perfectly, that is no proof.  

There are several different options for reconstructions. Most involved is making the object with accurate materials and only using techniques and tools that were (presumably) also used for making the original. This can be extremely costly and time-consuming, however - so for most reconstructions, compromises are made. In many cases, modern tools and methods are used, at least where there is no discernible influence on the end result - such as using modern drills or saws. In some cases, more of a deviation from the original is deemed acceptable, for instance when the aim is to give an impression of something that is only seen from a distance - or if the budget does not allow for anything closer to the original.

So reconstructions and archaeotechnique are quite closely connected to each other. Experimental archaeology, on the other hand, can have an overlap with both, but is a very clearly defined and distinct thing. An archaeological experiment is always designed around a question that it is (hopefully) going to answer. The methods and materials that are used during the experiment are not necessarily the ones used in historical times; it is more important that they allow the core question to be answered. During the last decade or so, "experimental archaeology" has become a bit of a buzzword - it's thus worth it to look a bit more closely if something is labeled as an archaeological experiment, as that is not always really the case.