Bash is an sh-compatible shell and command language for the GNU Project. I use this language at the Ubuntu operating system in combination with the GAMMA and SNAP softwares. More information here.
Hypertext Markup Language (HTML) is mostly used for the creation of web pages (this one included). In encountered this language while trying to automate processes for SNAP. For the site that helped understand better the language hit here.
By the same name goes the numerical computing environment and the proprietary programming language. MATLAB is designed for those who want to work on matrix mathematics with applications on data analysis, signal or image processing or other applications. More information here.
This language is a general-purpose language. Easy to learn and use yet reliable and with tons of libraries. Personally, I've been using Python to automate processes in ArcGIS. For the site that helped me better understand the language hit here.
R is a programming language and software environment for statistical computing and graphics, but most importantly it's free. More information here.
Structured Query Language is a domain-specific language used in programming and designed for managing data. Easy to use and broadly found in very large databases, GIS with geographic data included. Learn how to use it here.