The erf command computes the cumulative probability (probability that a variate assumes a value less than or equal to z) for a standard normal distribution (that is, with mean 0 and variance 1).

Other normal distributions can be modeled by re-normalizing (that is, erf((z-m)/s) is the probability distribution of a normal distribution with mean m and standard deviation s).

Note that this is not the same as Maple's top-level erf command.  It is synonymous with Statistics:-CDF( Normal(0,1), z, 'numeric').

$\mathrm{MapleTA}:-\mathrm{Builtin}:-\mathrm{erf}\left(0\right)$

$0.500000000000000$

$\mathrm{MapleTA}:-\mathrm{Builtin}:-\mathrm{erf}\left(0.62\right)$

$0.732371106531017$

The MapleTA[Builtin][erf] command was introduced in Maple 18.

For more information on Maple 18 changes, see Updates in Maple 18.