Lactobacillales vs LAB (Lactic acid bacteria)
Lactic acid fermentation is the most common type of fermentation among Eubacteria, and it's found on several genera. 

Actually, regarding the fermentation types, we can say as a general rule:


Ethanol fermentation: found in Plants and Fungi.
Lactic acid fermentation: found in Bacteria and Animals.


That being said, according to the Todar's Online Textbook of Bacteriology, 


  Although many genera of bacteria produce lactic acid as a primary or secondary end-product of fermentation, the term Lactic Acid Bacteria is conventionally reserved for genera in the Order Lactobacillales.


And according to Lactic Acid Bacteria: Microbiological and Functional Aspects, Fourth Edition:


  They [LAB] belong to the Phylum Firmicutes, Class Bacilli and Order Lactobacillales. 


These genera are: Lactobacillus, Leuconostoc, Pediococcus, Lactococcus, Streptococcus, Carnobacterium, Enterococcus, Oenococcus, Tetragenococcus, Vagococcus and Weisella.

The problem here is that not all lactic acid producing bacteria are called a LAB. Therefore, Lactobacillales and LAB can be used interchangeably. However, you cannot say that all bacteria that perform lactic acid fermentation are LAB. 

Sources: 


Textbookofbacteriology.net. (2017). Online Textbook of Bacteriology. [online] Available at: http://textbookofbacteriology.net/index.html [Accessed 3 May 2017].
Lactic Acid Bacteria: Microbiological and Functional Aspects, Fourth Edition
En.wikipedia.org. (2017). Lactobacillales. [online] Available at: https://en.wikipedia.org/wiki/Lactobacillales [Accessed 3 May 2017].