Metatrader 5 uses a programming language called MQL5 as opposed to the MQL4 used by Metatrader 4. The exciting thing about MQL5 is that it allows “black box” programming which, in a nutshell, means that it is easier to program and so will logically be a better framework for users and developers of trading robots and other expert advisors. However, MetaQuotes expanded this capability into MQL4 in 2014, so it is not a difference between the platforms any more, although there is a likelihood that if the language is upgraded at some time in the future, MetaQuotes will not extend any upgrades into MQL4 as well as MQL5