This improvement brings a second variant for the existing "attribute" function. The "attribute" function in previous QGIS releases required both a target feature and attribute name to be specified. The new version is much simpler, automatically using the current feature and only requiring an attribute name.
E.g.
Previous behavior:
attribute($currentfeature, 'name' )
-> returns value stored in 'name' attribute for the current feature
Improved behavior:
attribute( 'name' )
-> returns the value stored in 'name' attribute for the current feature
It's just a faster shorthand version!