Marketing, namely advertising (Facebook, Google ads, maybe magazines, etc.)
Despite all the nice words about "healthy, green, and socially responsible", the business of this company (and many, many similar ones) is not "providing information". It's affiliate marketing - getting people to click through to retail sites and buy stuff, on which the company earns commissions (often they also get paid for registrations).
In a very real sense, their product is customers. They sell paying customers to the retail sites, and before that, they basically have to buy "raw customers" through advertising. The times when you could rely on getting enough people to visit your website for free are largely over - there is too much competition for peoples' attention. They can only be profitable if they can get the raw customers cheap enough, and can convert enough of them to paying customers.
And this is really how it's talked about internally, in what is by now a highly organized industry: key performance measures are CPC (how much does it cost to get someone to come to your website), conversion rate (what percentage of visitors register) and ARPU (average revenue per user).