An additive adverb
Encoding Strategies:
linguistic

tan
so, as
+
bien
well
También means also and is literally tan0 (so, as0) + bien1 (well1). When someone is also doing something, it means they're doing it as well.
también
also, too, as well
Indicates that something applies equally to someone or something else already mentioned, just as well as the first.
Yo hablo español y mi hermana tambiénI speak Spanish and my sister does too.
También tengo un gato en casaI also have a cat at home.
Me gustaría ir, y a ella le gustaría tambiénI'd like to go, and she'd like to as well.