It means “carrier”。For example some computer chips cannot fit in the slots themselves but need a another bigger chip to fit in which then fits into the slot of the computer,in that sense,you call the bigger chip"载体".Or in medicine,some insects are the载体of some diseases.In your text it is a figurative expression.meaning the language is the"carrier"of the corresponding culture.

在信息技术和通信系统中， 通常把信息的发生者称为信源,信息的接受者称为信宿,传播信息的媒介称为载体。 在平日生活中，通常形容 承载知识或信息的物质形体。

载体就是工具，媒介的意思。语言是传达情感和信息的载体，"载"就是“装”的意思。情感和信息装在某句话里，通过这句话了解了情感和信息。那么这句话就发挥了作为情感和信息的载体的作用