Member alias

From DKPLP Doc

A member alias is a way to map alternative characters to the corresponding main characters and are defined in the member list dialog. Often one does not want to create one DKP account for every alt, so instead all DKP earned by an alt (or loot bought) should be transferred to the main. This is where member aliases come in.

A member alias of Foo to Bar tells the program that Foo is an alt of Bar, effectively making the program to replace any occurrence of Foo in the log with Bar. Hence if Foo was present during 20:00 to 21:00 then the parser will see it as if Bar was present during that time (and not Foo). The same goes for loot, if Foo bought loot then the parser sees it as if Bar bought it (and hence charges Bar with the price).