Answer

Version control is "the management of changes to documents, computer programs, large web sites, and other collections of information." (Wikipedia). It's a way that we can keep track of our projects across time, space, different users, and different systems!

But why learn version control techniques and software? The Software Carpentries Git lesson outlines some great reasons:

• Nothing that is committed to version control is ever lost, unless you work really, really hard at it. 
  • Since all old versions of files are saved, it’s always possible to go back in time to see exactly who wrote what on a particular day, or what version of a program was used to generate a particular set of results.
• We know who did what when.
  • As we have this record of who made what changes when, we know who to ask if we have questions later on, and, if needed, revert to a previous version, much like the “undo” feature in an editor.
• Collaboration is smoother.
  • When several people collaborate in the same project, it’s possible to accidentally overlook or overwrite someone’s changes. The version control system automatically notifies users whenever there’s a conflict between one person’s work and another’s.