What is the definition of "multivariate testing" I have seen job adverts that require experience in "multivariate testing". Although I have taken studied a bit statistics, I cant say for sure what this is. 
The almighty Wikipedia provides a vague answer, first results on google talk about multivariate testing when it comes to websites, and when I search litterature on Amazon for multivariate testing, there is no "Multivariate testing for dummies" and other results seem irrelevant. 
What would you say multivariate testing is (more specific in terms of statistics), and if you work with multivariate testing, what is it you do?
 A: Multivariate statistics deals with vector valued observations that can have some more general stochastic dependence within each vector. In contrast, univariate statistics is about data where each value is independent from each other. 
So in multivariate statistics, covariance matrices or copulas as models for dependence appear as an important property of the data. In univariate statistics, such words are not needed to describe the data, at most in the "internals" of some statistics. For example, the whole dataset of a large clinical study, where lots of parameters are measured on the probands, is multivariate data. 
Multivariate testing is testing with multivariate data, e.g. testing about correlations and regression models, testing differences of whole mean vectors, and multiple testing in which component the mean vectors differ. 
See the toc of some textbooks about multivariate statistics, e.g. Anderson or Muirhead.
A: Different statisticians use "multivariate statistics" to mean different things.
In a wider sense, "multivariate" refers to all procedures that analyse the relations between more than two variables. An example for this would be a two-way analysis of variance (two-way ANOVA), with two independent variables and one dependent variable.
In a more narrower sense, "multivariate" refers to all statistical procedures that examine more than one dependent variable. An example would be a multivariate analysis of variance (MANOVA), but not the aforementioned two-way ANOVA. This is the meaning that Wikipedia uses in the article on multivariate statistics, and it is also what I learned to think of as multivariate when I was taught statistics at university.
Multivariate statistics usually deals with complex, often layered real-world data and employs linear or mixed or generalized linear mixed models, principal component analysis, and so on.

Can you not deduce what your future employer expects from the job description, what they do (see the website), or simply call them and ask (the secretary)?
