People who are fluent in multiple languages can make money online in a couple of ways. Learn about being an online ESL teacher or about translating documents.
A “gig” in the online world is small work or projects you do as a freelancer using a particular online marketplace as a means to find work, book clients and get make money online. This work pays quite well ($25+/hour is quite common) is quite varied, including copywriting, painting, cleaning, software/website development, computer support, translations, putting together furniture, carpentry work and a lot else. This can be a great online side hustle for college students.
Businesses often need someone to translate their documents or presentations from one language. Someone who is proficient in multiple languages can register with an translating freelancer site and choose which jobs they want to work on.