BGP Standard Community
A standard BGP community is defined by a 32-bit number that can be included with a route within the BGP update. A community is actually an optional transitive attribute.
The term "standard" simply refers to the format of the field within the BGP message that contains this community number. This is in contrast to a extended BGP community format.
Links:
https://forum.networklessons.com/t/bgp-communities-explained/1239/86?u=lagapides
https://www.ciscopress.com/articles/article.asp?p=2756480&seqNum=12