The concept is called "mini programs", which works wherein users can call up useful information from third-party applications within the WeChat app, then use them instantly without the need of downloading and installation. Examples of the third-party apps are photo filters, language tools and ride-sharing services.
The mini programs solve two crucial problems plaguing the mobile apps model. The first problem is the increasing average size of mobile apps. This is because developers are packing in more features as well as media files to take advantage of better hardware and screens of modern smartphones.
This won't be a problem if the user has unlimited data and a brand new smartphone, but in emerging markets, consumers tend to use capped data plans and older phone models with less memory. Having said, apps with big sizes are inconvenient and less likely to be downloaded in the first place.
The second problem is the registration of users on an app, which makes smartphone users worldwide annoyed. Example are eCommerce applications, which requires the user to register their usernames, passwords, email addresses and payment information before the application will work.