According to spark documentation "where() is an alias for filter()"
filter(condition)
Filters rows using the given condition.
where() is an alias for filter().
Parameters: condition – a Column of types.BooleanType or a string of SQL expression.
>>> df.filter(df.age > 3).collect()
[Row(age=5, name=u'Bob')]
>>> df.where(df.age == 2).collect()
[Row(age=2, name=u'Alice')]
>>> df.filter("age > 3").collect()
[Row(age=5, name=u'Bob')]
>>> df.where("age = 2").collect()
[Row(age=2, name=u'Alice')]