1_ (jquery.js) vs (jquery.min.js).txt

"jquery.min.js" is a compressed version of "jquery.js" 

Both support the same functions. (In terms of functionality they are absolutely the same.)

"jquery.min.js":

      - whitespaces and comments removed\stripped out, 
      - shorter variable names, 
      - preserve bandwidth. 

"jquery.min.js" - It is recommended to use this compressed version in production environment.(websites)

"jquery.js"  -  It is recommended for developers, guys who needs to read, learn about or/and understand jquery codes